Radiographic image capturing system and radiographic image capturing method

ABSTRACT

In a radiographic image capturing system and radiographic image capturing method, in a case that at least two radiation sources are housed in a radiation output device, weighting of doses of respective radiation emitted from the at least two radiation sources is carried out. Thereafter, respective radiation is applied to a subject from the at least two radiation sources in accordance with the weighting. Then, the radiation detecting device detects the respective radiation that has passed through the subject and converts the detected radiation into a radiographic image.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Applications No. 2010-187298 filed on Aug. 24, 2010, No.2010-187300 filed on Aug. 24, 2010, No. 2010-187303 filed on Aug. 24,2010, No. 2011-179091 filed on Aug. 18, 2011, No. 2011-179092 filed onAug. 18, 2011 and No. 2011-179096 filed on Aug. 18, 2011, of which thecontents are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radiographic image capturing systemand a radiographic image capturing method for applying radiation from aplurality of radiation sources housed in a radiation output device to asubject, detecting radiation that has passed through the subject with aradiation detecting device, and converting the detected radiation intoradiographic images.

2. Description of the Related Art

In the medical field, there have widely been used radiographic imagecapturing systems, which apply radiation from a radiation source to asubject and detect the radiation that has passed through the subjectwith a radiation detecting device in order to acquire a radiographicimage of the subject. Radiographic image capturing systems that areinstalled in hospitals (medical organizations), for example, usuallyemploy a thermionic emission radiation source, which is relatively largeand heavy.

If such a radiographic image capturing system is directly used tocapture radiographic images within hospitals while making rounds, oroutside of hospitals, e.g., in medical checkup cars, at sites sufferingfrom natural disasters, or at sites receiving home care services, then alarge and heavy radiation source needs to be carried to such sites forcapturing radiographic images. The process of carrying the radiationsource to the site and setting up the radiation source at the site isquite burdensome for the doctor or radiological technician in charge. Tosolve this problem, Japanese Laid-Open Patent Publication No.2007-103016 discloses a field-emission radiation source, which issmaller and lighter than a thermionic emission radiation source.

SUMMARY OF THE INVENTION

If a field-emission radiation source is operated at a site, it is highlylikely that difficulties will be experienced in preparing an appropriateexternal power supply. Therefore, the field-emission radiation sourceshould preferably be of a battery-powered design. However, abattery-powered field-emission radiation source, although it is smalland lightweight, emits a small dose of radiation. It is customary forthe doctor or radiological technician to keep the field-emissionradiation source as closely to the subject as possible while capturing aradiographic image of the subject at a site, in order to reduce thesource-to-image distance (SID) between the field-emission radiationsource and the radiation detecting device. As a result, radiationemitted from the field-emission radiation source has a small irradiationrange. Because of the small irradiation range, and also due to the smalldose (exposure dose) of radiation applied to the subject, thefield-emission radiation source may fail to capture a radiation imagebased on an exposure dose that is sufficiently large for a doctor toread radiation images correctly.

One solution is to install a plurality of field-emission radiationsources and to emit radiation from such field-emission radiation sourcestoward a subject in order to cover a desired irradiation range (a regionto be imaged of the subject). According to another solution, while asingle field-emission radiation source is being moved over the subject,radiation is emitted toward the subject from the field-emissionradiation source, which has been moved to different positions in orderto cover a desired irradiation range.

As long as a subject is irradiated with an optimum dose (exposure dose)of radiation depending on the subject, a radiographic image of thesubject can be captured based on an exposure dose that is large enoughfor a doctor to read the resultant radiation image correctly, and thesubject remains free of undue radiation exposure.

However, as noted above, if a field-emission radiation source simplyapplies radiation to a subject in order to cover a desired irradiationrange, the subject may not necessarily be irradiated with an optimumdose of radiation.

An object of the present invention is to provide a radiographic imagecapturing system and a radiographic image capturing method, which arecapable of easily increasing an irradiation range of radiation, and ofapplying an optimum dose of radiation to a subject, in the case that aradiographic image of the subject is captured using a field-emissionradiation source at a short SID.

To accomplish the above object, in accordance with the presentinvention, there is provided a radiographic image capturing systemcomprising:

a radiation output device housing therein at least two radiation sourcesfor emitting radiation;

a radiation detecting device for detecting radiation that has passedthrough a subject and converting the detected radiation into aradiographic image, in a case where each of the at least two radiationsources applies the radiation to the subject; and

a control device for controlling the radiation output device and theradiation detecting device,

wherein the control device carries out prescribed weighting of doses ofradiation to be emitted from the at least two radiation sources, andcontrols the radiation output device to apply the doses of the radiationfrom the at least two radiation sources to the subject in accordancewith the weighting.

According to the present invention, there also is provided aradiographic image capturing method comprising the steps of:

in a case that at least two radiation sources for emitting radiation arehoused in a radiation output device, carrying out weighting of doses ofradiation to be emitted from the at least two radiation sources;

applying the radiation to the subject from the at least two radiationsources in accordance with the weighting; and

with the radiation detecting device, detecting the radiation that haspassed through the subject and converting the detected radiation into aradiographic image.

According to the present invention, an irradiation range of theradiation is not set simply by enabling a desired irradiation range(region to be imaged of the subject) to be covered, but rather,radiation doses of the respective radiation emitted from at least tworadiation sources are weighted, and thereafter the respective radiationis applied to the subject from the at least two radiation sources.

Accordingly, with the present invention, even if image capturing of aradiographic image is carried out with respect to the subject at a shortSID using field-emission radiation sources, the irradiation range of theradiation can easily be enlarged, and radiation can be applied at anoptimum radiation dose (exposure dose) with respect to the subject. As aresult, a radiographic image suitable for diagnostic interpretation by adoctor can be obtained, and unnecessary exposure of the subject toradiation can be avoided.

Further, the present invention (the first through third inventionsthereof) can be constituted in the following manner.

In the first invention, the radiation output device houses therein atleast three radiation sources, and the at least three radiation sourcesare grouped into at least three groups each including at least one ofthe radiation sources.

Under the above condition, the control device carries out, with respectto the groups, the weighting of the doses of radiation to be emittedfrom the at least three radiation sources, such that the dose of theradiation emitted from the radiation source included in the grouppositioned near a geometric center position of the at least threeradiation sources is of a maximum dose level, and the doses of radiationemitted from the radiation sources included in the groups other than thegroup positioned near the geometric center position are of a lower doselevel of a degree for supplementing the maximum dose level.

Then, the control device controls the radiation output device to applythe radiation to the subject from the at least three radiation sourcesin accordance with the weighting.

In the foregoing manner, with the first invention, since the radiationsources are grouped into at least three groups, and weighting of thedoses of the respective radiation is carried out with respect to thegroups, even if image capturing of a radiographic image is carried outwith respect to the subject at a short SID using field-emissionradiation sources, the irradiation range of the radiation can easily beenlarged, and radiation can be applied at an optimum radiation dose(exposure dose) with respect to the subject. In this case as well, byirradiating the subject with radiation at an optimum dose depending onthe subject, a radiographic image suitable for diagnostic interpretationby a doctor can be obtained, and unnecessary exposure of the subject toradiation can be avoided.

Also, according to the first invention, in a case where the subject isdisposed between the radiation output device and the radiation detectingdevice, and a region to be imaged of the subject is positioned so as toface the geometric center position, the doses of radiation emitted fromthe radiation sources included in the group, which is positioned nearthe geometric center position, are of a maximum dose level, whereas thedoses of radiation emitted from the radiation sources included in thegroups other than the group positioned near the geometric centerposition, are of a lower dose level. Therefore, with respect to arelatively small region to be imaged (e.g., a hand), a radiographicimage capturing process can be performed efficiently.

In the second invention, the radiation output device houses therein atleast three radiation sources, and the at least three radiation sourcesare grouped into at least three groups each including at least one ofthe radiation sources.

In this case, the control device carries out, with respect to thegroups, the weighting of the doses of radiation to be emitted from theat least three radiation sources, such that the doses of radiationemitted from the radiation sources included in the groups positioned atboth sides of a geometric center position of the at least threeradiation sources are of a maximum dose level, and the dose of radiationemitted from the radiation source included in the group positioned nearthe geometric center position is of a lower dose level of a degree forsupplementing the maximum dose level.

Then, the control device controls the radiation output device to applythe radiation to the subject from the at least three radiation sourcesin accordance with the weighting.

In the foregoing manner, with the second invention, as in the firstinvention, since the radiation sources are grouped into at least threegroups, and weighting of the doses of the respective radiation iscarried out with respect to the groups, even if image capturing of aradiographic image is carried out with respect to the subject usingfield-emission radiation sources, the irradiation range of the radiationcan easily be enlarged, and radiation can be applied at an optimumradiation dose (exposure dose) with respect to the subject. Also, aradiographic image suitable for diagnostic interpretation by a doctorcan be obtained, and unnecessary exposure of the subject to radiationcan be avoided.

Also, in the second invention, in a case where the subject is disposedbetween the radiation output device and the radiation detecting device,and a region to be imaged of the subject is positioned so as to face thegeometric center position, the doses of radiation emitted from theradiation sources included in the groups, which are positioned at bothsides of the geometric center position, are of a maximum dose level,whereas the doses of radiation emitted from the radiation sourcesincluded in the groups, which are positioned near the geometric centerposition, are of a lower dose level. Therefore, unlike the firstinvention, with respect to a relatively large region to be imaged (e.g.,chest), a radiographic image capturing process can be performedefficiently.

Incidentally, in the first and second inventions, in a case where thereis a group including at least two radiation sources, if additionalweighting is carried out on the radiation sources included in the group,then it is possible to apply radiation to the subject at an optimum dosemore accurately.

Next, in the third invention, in a case that a first image capturingprocess is carried out, in which radiation is applied to the subjectfrom at least one radiation source from among the at least two radiationsources, the radiation detecting device detects radiation that haspassed through the subject, thereby acquiring a first radiographic imageby the first image capturing process.

Then, the control device carries out the weighting of the doses ofradiation to be emitted from the at least two radiation sources so as tosupplement an insufficiency in the dose of radiation, in a case that thedose of radiation by the first image capturing process shown in thefirst radiographic image does not reach an optimum dose with respect tothe subject, and controls the radiation output device to carry out asecond image capturing process, in which the respective radiation isapplied to the subject from the at least two radiation sources, inaccordance with the weighting.

According to the third invention, the first image capturing process isperformed by use of the at least one radiation source, and if the doseof radiation (exposure dose) with respect to the subject shown in theradiographic image (first radiographic image) obtained by the firstimage capturing process does not reach the optimum radiation dose, therespective radiation doses of radiation emitted from the at least tworadiation sources during the second image capturing process areweighted, in order to supplement any difference (insufficiency in theradiation dose) between the optimum radiation dose and the dose appliedduring the first image capturing process.

Accordingly, even if image capturing is carried out a second time withrespect to the subject, the cumulative exposure dose with respect to thesubject by the initial image capturing process and the retaken imagecapturing process (i.e., the first and second image capturing processes)is made to correspond with the optimum radiation dose.

More specifically, with the third invention, even in the event thatimage capturing is performed again with respect to the subject (in thesecond image capturing process) due to the fact that a desiredradiographic image was not obtained by the first image capturingprocess, the subject is not exposed to radiation unnecessarily. Further,using the first radiographic image and the second radiographic imageobtained from the second image capturing process, assuming desired imageprocessing (e.g., an addition process) is performed, a radiographicimage based on an exposure dosage suitable for diagnostic interpretationby a doctor can easily be obtained.

As described above, in the third invention, an irradiation range of theradiation is not set simply by enabling a desired irradiation range(region to be imaged of the subject) to be covered, but rather,radiation doses of the respective radiation emitted from the radiationsources during the second image capturing process are weighted based onthe first radiographic image. Accordingly, even if the first and secondimage capturing processes are carried out with respect to the subjectusing field-emission radiation sources, the irradiation range of theradiation can easily be enlarged, and radiation can be applied at anoptimum radiation dose (exposure dose) with respect to the subject.

Incidentally, in the third invention, in a case where the dose ofradiation indicated in the first radiographic image has reached theoptimum radiation dose, the first radiographic image already is aradiographic image of an exposure dose sufficient for diagnosticinterpretation by the doctor, and thus naturally, carrying out of thesecond image capturing process (recapturing) becomes unnecessary.

In the first through third inventions, in a case that the radiationoutput device and the radiation detecting device face each other, theradiation output device houses therein the at least two radiationsources (or at least three radiation sources) arranged in a linear arrayor at least three radiation sources arranged in a two-dimensionalmatrix, with respect to an irradiated surface of the radiation detectingdevice that is irradiated with radiation. In this case, capturing ofradiographic images can be carried out effectively with respect to anytype of region to be imaged.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which preferredembodiments of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a radiographic image capturing systemaccording to a first embodiment of the present invention;

FIG. 2A is a perspective view of a radiation output device and aradiation detecting device shown in FIG. 1, which are integrallycombined with each other;

FIG. 2B is a perspective view of the radiation output device and theradiation detecting device, in a state of being separated from eachother;

FIGS. 3A and 3B are plan views showing how regions to be imaged of asubject are positioned with respect to the radiation detecting device;

FIGS. 4A and 4B are perspective views of the radiation output device;

FIGS. 5A and 5B are side elevational views showing the manner in which aregion to be imaged of the subject is irradiated;

FIG. 6 is a block diagram of the radiation output device and theradiation detecting device shown in FIG. 1;

FIG. 7 is a block diagram of a control device shown in FIG. 1;

FIG. 8 is a diagram of a circuit arrangement of the radiation detectingdevice shown in FIG. 6;

FIG. 9 is a diagram showing, by way of example, a table that is storedin the database shown in FIG. 7;

FIG. 10 is a diagram showing, by way of example, a table that is storedin the database shown in FIG. 7;

FIG. 11 is a flowchart of an operation sequence of the radiographicimage capturing system shown in FIG. 1;

FIGS. 12A and 12B are side elevational views of a radiographic imagecapturing system according to a first modification;

FIGS. 13A and 13B are side elevational views of a radiographic imagecapturing system according to a second modification;

FIGS. 14A and 14B are perspective views of a radiographic imagecapturing system according to a third modification;

FIGS. 15A and 15B are perspective views of a radiographic imagecapturing system according to a fourth modification;

FIG. 16 is a cross sectional view showing a radiographic image capturingsystem according to a fifth modification;

FIG. 17 is a cross sectional view showing in outline the structure of asignal output section of one pixel of a radiation detector of FIG. 16.

FIG. 18A is an outline explanatory diagram showing schematically anexample of a radiographic image capturing system according to a sixthmodification;

FIG. 18B is an outline explanatory diagram showing an example of ascintillator illustrated in FIG. 18A;

FIG. 19 is a schematic view of a radiographic image capturing systemaccording to a second embodiment of the present invention;

FIGS. 20A and 20B are perspective views of a radiation output deviceshown in FIG. 19;

FIGS. 21A and 21B are side elevational views showing the manner in whicha region to be imaged of the subject is irradiated;

FIGS. 22A and 22B are side elevational views showing the manner in whicha region to be imaged of the subject is irradiated;

FIG. 23 is a block diagram of the radiation output device and theradiation detecting device shown in FIG. 19;

FIG. 24 is a block diagram of a control device shown in FIG. 19;

FIG. 25 is a diagram showing, by way of example, object data that isstored in a database shown in FIG. 24;

FIG. 26 is a diagram showing, by way of example, a table that is storedin the database shown in FIG. 24;

FIG. 27 is a flowchart of an operation sequence of the radiographicimage capturing system shown in FIG. 19;

FIG. 28 is a flowchart of an operation sequence of the radiographicimage capturing system shown in FIG. 19;

FIGS. 29A and 29B are side elevational views of a radiographic imagecapturing system according to a seventh modification;

FIGS. 30A and 30B are perspective views of a radiographic imagecapturing system according to a eighth modification;

FIGS. 31A and 31B are explanatory diagrams of a radiographic imagecapturing system according to a ninth modification;

FIG. 32 is a side elevational view showing in outline a radiographicimage capturing system according to a tenth modification;

FIG. 33 is a block diagram showing a radiographic image capturing systemaccording to an eleventh modification;

FIG. 34 is a block diagram showing a radiographic image capturing systemaccording to an eleventh modification;

FIG. 35 is a flowchart of an operation sequence of the radiographicimage capturing system according to eleventh and twelfth modifications;

FIG. 36 is a block diagram showing a radiographic image capturing systemaccording to the twelfth modification;

FIGS. 37A and 37B are side elevational views showing image capturing bya camera with respect to a region to be imaged of the subject;

FIG. 38 is a flowchart of another operation sequence of the radiographicimage capturing system according to the eleventh and twelfthmodifications;

FIG. 39 is a side elevational view showing a radiographic imagecapturing system according to a thirteenth modification;

FIG. 40 is a side elevational view showing a radiographic imagecapturing system according to a fourteenth modification; and

FIGS. 41A and 41B are side elevational views illustrating a situation inwhich a fifteenth modification is applied to the second embodiment,whereby application of radiation is implemented with respect to a regionto be imaged of the subject.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A radiographic image capturing system according to preferred embodimentsof the present invention, in relation to a radiographic image capturingmethod, will be described in detail below with reference to FIGS. 1through 41B.

[Structures of First Embodiment]

As shown in FIG. 1, a radiographic image capturing system 10A accordingto a first embodiment of the present invention includes a radiationoutput device 20 housing therein a plurality of radiation sources 18 athrough 18 g, which are capable of applying radiation 16 a through 16 gto a subject 14 lying on an image capturing table 12 such as a bed orthe like, a radiation detecting device 22 for detecting radiation 16 athrough 16 g that has passed through the subject 14 and converting thedetected radiation into radiographic images, and a control device 24 forcontrolling the radiation output device 20 and the radiation detectingdevice 22. The control device 24, the radiation output device 20, andthe radiation detecting device 22 may send signals to each other andreceive signals from each other by way of a wireless LAN according tostandards such as UWB (Ultra-Wide Band), IEEE802.11.a/g/n. or the like,wireless communications using millimeter waves, or by wiredcommunications using cables.

The radiographic image capturing system 10A may be applied in order tocapture radiographic images of the subject 14 (patient) in an imagecapturing chamber of a radiological department of a hospital (medicalorganization), to capture radiographic images of the subject 14(patient) in a patient's bedroom in a hospital at the time that thedoctor 26 makes rounds, or to capture radiographic images of the subject14 outside of the hospital. Capturing of radiographic images of thesubject 14 outside of the hospital refers to capturing of radiographicimages of the subject 14 (examinee) at the time that a medical checkupis carried out using a medical checkup car, capturing of radiographicimages of the subject 14 (injured party) at a disaster site such as anatural disaster site, or capturing of radiographic images of thesubject 14 (resident) at a home medical care site.

To realize such applications, each of the radiation sources 18 a through18 g of the radiographic image capturing system 10A according to thefirst embodiment should preferably be a field-emission radiation source,as disclosed in Japanese Laid-Open Patent Publication No. 2007-103016.Further, the radiation output device 20, which houses therein theradiation sources 18 a through 18 g, has a grip 28 to be gripped by thedoctor or radiological technician in charge (hereinafter simply referredto as “doctor”), on a side thereof remote from the side on whichradiation 16 a through 16 g is emitted from the radiation sources 18 athrough 18 g. Therefore, the radiation output device 20 comprises aportable device.

The radiation detecting device 22 comprises a portable electroniccassette incorporating either a radiation detector of an indirectconversion type including a scintillator for temporarily convertingradiation 16 a through 16 g into visible light, or a solid-statedetector (hereinafter also referred to as “pixels”), which is made of asubstance such as amorphous silicon (a-Si) or the like, for convertingvisible light into electric signals. Alternatively, the radiationdetecting device 22 comprises a radiation detector of a directconversion type including a solid-state detector, which is made of asubstance such as amorphous selenium (a-Se) or the like, for directlyconverting radiation 16 a through 16 g into electric signals.

The control device 24 should preferably be a portable informationterminal such as a laptop personal computer (PC), a tablet PC, or apersonal digital assistant (PDA), for example. If the radiographic imagecapturing system 10A is used in an image capturing chamber of theradiological department of a hospital, then the control device 24 maycomprise a stationary console, while the radiation output device 20 andthe radiation detecting device 22 may be portable devices.

As shown in FIGS. 2A and 2B, the radiation detecting device 22 includesa rectangular housing 30 made of a material permeable to radiation 16 athrough 16 g (see FIG. 1) and having a surface (upper surface) forpositioning the subject 14 thereon, the surface serving as an irradiatedsurface 32, which is irradiated with radiation 16 a through 16 g. Theirradiated surface 32 has guide lines 34 serving as a reference for animage capturing area and an image capturing position for the radiation16 a through 16 g. The guide lines 34 provide an outer frame defining animaging area 36, which can be irradiated with radiation 16 a through 16g.

One side of the housing 30 has a switch 38 for turning on and off theradiation detecting device 22, a card slot 40 for receiving a memorycard (not shown) therein, an input terminal 42 for connection to an ACadapter, and a USB terminal 44 for connection to a USB cable (notshown).

The radiation detecting device 22 also includes holders 35, 37 thatproject outwardly from a side of the housing 30 remote from the sidehaving the switch 38, the card slot 40, the input terminal 42, and theUSB terminal 44. The holder 35 has a convex connection terminal 39facing the holder 37, whereas the holder 37 has a concave connectionterminal 41 facing the holder 35 (see FIGS. 2B to 3B). Theaforementioned radiation output device 20 has a hollow cylindricalcasing 46 including a concave connection terminal 43 on an end thereoffor receiving therein the convex connection terminal 39 of the holder35, and a convex connection terminal 45 on the other end thereof forbeing fitted into the concave connection terminal 41 of the holder 37(see FIGS. 2B, 4A and 4B).

By interfitting engagement of the connection terminals 39, 43 and theconnection terminals 41, 45, as shown in FIG. 2A, the radiation outputdevice 20 is held between the holders 35, 37, and the connectionterminals 39, 43 and the connection terminals 41, 45 are electricallyconnected to each other. In this manner, once the radiation outputdevice 20 and the radiation detecting device 22 are integrally combinedwith each other, the doctor 26 can grip the grip 28, for example, andcarry the radiation output device 20 and the radiation detecting device22. Further, while the radiation output device 20 and the radiationdetecting device 22 are integrally combined with each other, a locationon the radiation output device 20 where radiation 16 a through 16 g isemitted faces toward a side surface of the housing 30 of the radiationdetecting device 22.

On the other hand, by releasing the held state of the radiationdetecting device 22 by the holders 35, 37 and the connection terminals39, 41, 43, 45, and separating the radiation detecting device 22 fromthe radiation output device 20, the radiation output device 20 and theradiation detecting device 22 are no longer integrally combined witheach other, and the connection terminals 39, 43 and the connectionterminals 41, 45 are electrically disconnected from each other,respectively.

As shown in FIGS. 3A and 3B, for positioning the subject 14, as viewedin plan, a region to be imaged of the subject 14 is positioned such thata central position of the region to be imaged of the subject 14 and acentral position (i.e., a point of intersection of the guide lines 34)of the imaging area 36 are kept in substantial alignment with eachother, and the region to be imaged of the subject 14 falls within theimaging area 36. FIG. 3A shows the chest of the subject 14, which ispositioned as a region to be imaged. FIG. 3B shows a right hand of thesubject 14, which is positioned as a region to be imaged.

As shown in FIGS. 4A and 4B, the radiation output device 20 includes thehollow cylindrical casing 46, which is made of a material permeable toradiation 16 a through 16 g. Seven field-emission radiation sources 18 athrough 18 g are arranged along one direction, i.e., arranged as alinear array, in the casing 46. A USB terminal 50 for connection to aUSB cable (not shown) and the connection terminal 43 are disposed on oneend of the casing 46, whereas the connection terminal 45 is disposed onthe other end of the casing 46. The aforementioned grip 28 is disposedon a side surface of the casing 46, and incorporates therein a touchsensor (gripped state sensor) 52.

The touch sensor 52 comprises an electrostatic capacitance sensor or aresistance-film contact sensor. In a case where the doctor 26 grips thegrip 28 and contacts electrodes (not shown) of the touch sensor 52 withthe hand, the touch sensor 52 outputs a detection signal indicating thatthe hand and the electrodes are held in contact with each other. Thetouch sensor 52 may alternatively be a mechanical switch such as a pushswitch or the like. If the touch sensor 52 is a mechanical switch, thenin a case where the doctor 26 grips the grip 28 and contacts themechanical switch, the touch sensor 52 outputs a detection signalindicating that the mechanical switch has been turned on or off.

In a case where the doctor 26 grips the grip 28 and orients theradiation output device 20 toward the subject 14, the radiation outputdevice 20, in response to output of the detection signal from the touchsensor 52, enables radiation 16 a through 16 g to be emittedsimultaneously or sequentially from the respective radiation sources 18a through 18 g (see FIG. 4B). While the radiation output device 20 andthe radiation detecting device 22 are integrally combined with eachother by the holders 35, 37 and the connection terminals 39, 41, 43, 45,the radiation output device 20 does not permit the radiation sources 18a through 18 g to emit radiation, i.e., the radiation sources 18 athrough 18 g are prohibited from emitting radiation 16 a through 16 g,even if the doctor 26 grips the grip 28.

FIG. 5A shows the manner in which an image of the chest of the subject14, which is a relatively large region to be imaged, is captured,whereas FIG. 5B shows the manner in which an image of a hand of thesubject 14, which is a relatively small region to be imaged, iscaptured.

The seven radiation sources 18 a through 18 g are arranged in the casing46 of the radiation output device 20 along a horizontal direction ofFIGS. 5A and 5B, i.e., along the longitudinal direction of the casing46. The geometric center position of the radiation sources 18 a through18 g is the position of the central radiation source 18 d (the centerposition of the casing 46). In the radiation output device 20, theradiation sources 18 a through 18 g are grouped into three groups 54,56, 58. In this case, the two radiation sources 18 a, 18 b belong to(i.e., are included in) the group 54, the three radiation sources 18 cthrough 18 e belong to the group 56, and the other two radiation sources18 f, 18 g belong to the group 58. Thus, the group 56 containing thecentral radiation source 18 d is referred to as a central group, whichincludes the geometric center position, while each of the groups 54, 58is referred to as a side group, which is positioned at each side of thegeometric center position.

Incidentally, if the portable radiation output device 20 is operated ina hospital or at a site outside of a hospital, then since difficulty maybe experienced in securing an appropriate external power supply, each ofthe radiation sources 18 a through 18 g of the radiation output device20 should preferably be a battery-powered radiation source.Consequently, the field-emission radiation sources 18 a through 18 gshould be small and lightweight radiation sources, for emitting asmaller dose of radiation than is possible with a thermionic emissionradiation source, which typically is used in an image capturing chamberof the radiological department of the hospital.

In this case, at the site where the radiographic image capturing systemis used, the doctor 26 is required to keep the radiation output device20 as close to the subject 14 as possible, thereby reducing thesource-to-image distance (SID) between the radiation sources 18 athrough 18 g and the radiation detector 60 in the radiation detectingdevice 22, for capturing radiographic images of the subject 14. As aresult, radiation 16 a through 16 g emitted from the respectiveradiation sources 18 a through 18 g is applied within a narrowirradiation range, and the doses (exposure doses) of radiation 16 athrough 16 g applied to the subject 14 are small. Therefore, theradiographic image capturing system 10A may fail to capture radiationimages based on an exposure dose, which is large enough to enable thedoctor 26 to read radiation images correctly.

In the first embodiment, at least three radiation sources (sevenradiation sources 18 a through 18 g in FIGS. 4A through 5B) are disposedin the radiation output device 20. Further, portions of the irradiationranges of radiation (radiation 16 a through 16 g shown in FIGS. 4Bthrough 5B) emitted from adjacent radiation sources overlap mutuallywith each other, so that radiation is applied, without gaps, withrespect to the region to be imaged of the subject 14.

Also, if the subject 14 is irradiated with an optimum dose (exposuredose) of radiation depending on the region to be imaged of the subject14, the thickness thereof, etc., then a radiographic image can beobtained based on an exposure dose, which is suitable to enable thedoctor 26 to diagnostically interpret the resultant radiation imagecorrectly, and together therewith, the subject 14 can avoid undueexposure to radiation.

In the first embodiment, all of the radiation sources incorporated inthe radiation output device 20 are grouped into at least three groupseach including at least one radiation source (three groups 54, 56, 58 inFIGS. 5A and 5B). Then, after weighting of the doses of radiation iscarried out with respect to the groups depending at least on the regionto be imaged of the subject 14, radiation is applied to the subject 14from the radiation sources according to the weighting.

More specifically, during image capturing of a radiographic image withrespect to a comparatively large region to be imaged (the chest) asshown in FIG. 5A, so that radiation 16 a through 16 g is applied to theentire chest region as a whole, it is required that radiation 16 athrough 16 g be applied over a comparatively wide range (i.e., theentire imaging area 36). Additionally, concerning the cumulativeexposure dose applied to the subject 14 in the image capturing process,an optimum radiation dose is needed (i.e., an exposure dose suitable forenabling diagnostic interpretation by the doctor 26) corresponding tothe aforementioned chest region and the thickness thereof.

Consequently, with the first embodiment, in an image capturing processcarried out with respect to a comparatively large region to be imaged asshown in FIG. 5A, weighting is carried out with respect to the groups,such that the doses of radiation 16 a, 16 b, 16 f, 16 g emitted from theradiation sources 18 a, 18 b, 18 f, 18 g of the side groups 54, 58 aremaximum (shown by the thick one-dot-dashed lines in FIG. 5A), whereasthe doses of radiation 16 c through 16 e emitted from the radiationsources 18 c through 18 e of the central group 56 are smaller, of adegree sufficient to supplement the maximum dose level (shown by thethin one-dot-dashed lines in FIG. 5A). In accordance with suchweighting, the respective radiation sources 18 a through 18 g emitradiation 16 a through 16 g simultaneously or sequentially, or therespective groups emit radiation 16 a through 16 g sequentially.

On the other hand, in an image capturing process with respect to acomparatively small region (the right hand) as shown in FIG. 5B, sincethe right hand is positioned in a central portion inside of the imagingarea 36, radiation 16 a through 16 g may be applied reliably only to acomparatively narrow area that includes the aforementioned centralportion. In this case as well, the cumulative exposure dose with respectto the subject 14 during the image capturing process must be an optimumdose (i.e., an exposure does suitable for diagnostic interpretation bythe doctor 26) corresponding to the right hand, the thickness thereof,etc.

Consequently, with the first embodiment, in the image capturing processwith respect to the comparatively small region to be imaged shown inFIG. 5B, weighting is carried out with respect to the groups, such thatthe doses of radiation 16 c through 16 e emitted from the radiationsources 18 c through 18 e of the central group 56 are maximum (shown bythe bold one-dot-dashed lines in FIG. 5B), whereas the doses ofradiation 16 a, 16 b, 16 f, 16 g emitted from the radiation sources 18a, 18 b, 18 f, 18 g of the side groups 54, 58 are smaller, of a degreesufficient to supplement the maximum dose level (shown by the fineone-dot-dashed lines in FIG. 5B). In accordance with such weightings,the respective radiation sources 18 a through 18 g emit radiation 16 athrough 16 g simultaneously or sequentially, or the respective groupsemit radiation 16 a through 16 g sequentially.

In the above explanations, the maximum radiation dose is defined as aradiation dose that is comparatively largest in the case that the dosesof radiation 16 a through 16 g are compared, and the smaller radiationdose is defined as a radiation dose that is comparatively smaller in thecase that the doses of radiation 16 a through 16 g are compared, suchthat none of the doses is in excess of the optimum radiation dose. Morespecifically, according to the first embodiment, in one-time imagecapturing process of FIGS. 5A and 5B, the doses of radiation 16 athrough 16 g emitted from the respective radiation sources 18 a through18 g of the respective groups 54, 56, 58 are weighted with respect tothe groups, such that the cumulative exposure dose, at the time that thesubject 14 is exposed to radiation by respectively applying theradiation 16 a through 16 g, becomes the optimum dose.

Additionally, in a case where weighting of the doses of radiation iscarried out with respect to the groups, additional weighting may becarried out with respect to the radiation sources of each group thatincludes at least two radiation sources. More specifically, in the firstembodiment, weighting may be carried out such that all the radiationsources of one group are weighted with the same dose of radiation, orsuch that the radiation sources of one group are weighted with differentdoses of radiation. In the case where additional weighting is carriedout with respect to the respective radiation sources, radiation can beapplied to the subject 14 more accurately.

Furthermore, since the time needed for image capturing of the subject 14is shortened thereby, it is preferable for radiation 16 a through 16 gto be applied simultaneously from the respective radiation sources 18 athrough 18 g. However, cases are known to occur in which it is difficultfor radiation 16 a through 16 g to be applied simultaneously, inaccordance with the ability to supply electric power to the radiationsources 18 a through 18 g (consumption of electric power in theradiation output device 20), or the image capturing conditions (numberof images to be captured) of the subject 14.

In such cases, the radiation sources 18 a through 18 g may sequentiallyapply radiation 16 a through 16 g respectively, so as to reliablycapture a radiographic image of the subject 14. If the radiation sources18 a through 18 g sequentially apply radiation 16 a through 16 grespectively, then a central portion of the region to be imaged, whichhas been positioned, may be irradiated initially, and thereafter, otherportions may be irradiated, for thereby lessening blurring of theradiographic image, which may be caused by movement of the region to beimaged during the image capturing process. Alternatively, the region tobe imaged may be irradiated initially with radiation, as indicated bythe thick one-dot-dashed lines in FIGS. 5A and 5B, and then beirradiated with radiation, as indicated by the thin one-dot-dashed linesshown in FIGS. 5B and 6B.

Accordingly, with the first embodiment, simultaneous or sequentialapplication of radiation 16 a through 16 g may be selected depending onthe ability to supply electric power to the radiation sources 18 athrough 18 g and image capturing conditions of the subject 14.

In the case that radiation 16 a through 16 g, the doses of which havebeen weighted in the foregoing manner, is applied to the image capturingregion of the subject 14, such radiation 16 a through 16 g passesthrough the region to be imaged and then through the surface (theimaging area 36 in FIGS. 2 through 3B) of the housing 30 of theradiation detecting device 22, and the radiation is led to a radiationdetector 60 housed in the interior of the housing 30. The radiationdetector 60, which is either a radiation detector of an indirectconversion type or a radiation detector of a direct conversion type,detects radiation 16 a through 16 g and converts the radiation 16 athrough 16 g into a radiographic image.

Internal details of the radiation output device 20, the radiationdetecting device 22, and the control device 24 of the radiographic imagecapturing system 10A will be described in detail below with reference tothe block diagrams shown in FIGS. 6 and 7 and the circuit diagram ofFIG. 8.

The radiation output device 20 further includes a communication unit 64for sending signals to and receiving signals from the control device 24by way of wireless communications through an antenna 62, a radiationsource controller 66 for controlling the radiation sources 18 a through18 c individually or by the groups, and a battery 68 for supplyingelectric power to various components of the radiation output device 20.

The battery 68 supplies electric power at all times to the touch sensor52, the communication unit 64, and the radiation source controller 66.In a case where the touch sensor 52 outputs a detection signal to theradiation source controller 66, at a time that the doctor 26 grips thegrip 28, the radiation source controller 66 controls the battery 68 inorder to supply electric power to various components of the radiationoutput device 20.

In a state in which the connection terminals 39, 43 and the connectionterminals 41, 45 are electrically connected to each other, and theradiation output device 20 and the radiation detecting device 22 areintegrally combined with each other, the battery 68 can be charged bythe battery 76 of the radiation detecting device 22. At this time, theradiation source controller 66 does not permit the battery 68 to supply,i.e., prohibits the battery 68 from supplying, electric power to theradiation sources 18 a through 18 g, even if a detection signal isreceived from the touch sensor 52. Accordingly, the radiation sourcecontroller 66 controls the battery 68 in order to start supply ofelectric power to the radiation sources 18 a through 18 g, in responseto a detection signal received from the touch sensor 52 in a state wherethe connection terminals 39, 43 and the connection terminals 41, 45 areelectrically disconnected from each other so that the radiation outputdevice 20 and the radiation detecting device 22 are separated from eachother.

If a cable (not shown) such as a communication cable, a USB cable, or acable according to IEEE1394, is connected to the radiation output device20, then the radiation output device 20 can send signals to and receivesignals from an external circuit, or may be supplied with electric powervia the cable. For example, if a USB cable (not shown) is connected tothe USB terminal 50, for example, then the battery 68 can be charged byelectric power supplied from an external circuit via the USB cable, andthe communication unit 64 can send signals to and receive signals froman external circuit via the USB cable.

The radiation detecting device 22 further includes a communication unit72 for sending signals to and receiving signals from the control device24 by way of wireless communications through an antenna 70, a cassettecontroller 74 for controlling the radiation detector 60, and a battery76 for supplying electric power to various components of the radiationdetecting device 22.

The battery 76 supplies electric power at all times to the cassettecontroller 74 and the communication unit 72. If the doctor 26 operates(turns on) the switch 38, the battery 76 is capable of supplyingelectric power to various components of the radiation detecting device22.

If a cable (not shown) such as a communication cable, a USB cable, or acable according to IEEE1394, is connected to the radiation detectingdevice 22, then the radiation detecting device 22 can send signals toand receive signals from an external circuit, or can be supplied withelectric power via the cable. For example, if a USB cable (not shown) isconnected to the USB terminal 44, for example, then the battery 76 canbe charged by electric power supplied from an external circuit via theUSB cable, and the communication unit 72 can send signals to and receivesignals from an external circuit via the USB cable.

The cassette controller 74 includes an address signal generator 78 forsupplying address signals to the radiation detector 60 for reading aradiographic image, an image memory 80 for storing the radiographicimage read from the radiation detector 60, and a cassette ID memory 82for storing cassette ID information, which identifies the radiationdetecting device 22.

A circuit arrangement of the radiation detecting device 22, in which theradiation detector 60 is of an indirect conversion type, will bedescribed in detail below with reference to FIG. 8.

The radiation detector 60 comprises an array of thin-film transistors(TFTs) 98 arranged in rows and columns, and a photoelectric conversionlayer 96 including pixels 90 and made of a material such as amorphoussilicon (a-Si) or the like for converting visible light into electricsignals. The photoelectric conversion layer 96 is disposed on the arrayof TFTs 98. In a case that radiation is applied to the radiationdetector 60, the pixels 90, which are supplied with a bias voltage Vbfrom the battery 76 (see FIG. 6), generate electric charges byconverting visible light into analog electric signals, and then storethe generated electric charges. Then, as a result of the TFTs 98 beingturned on along each row at a time, the stored electric charges can beread from the pixels 90 as an image signal.

The TFTs 98 are connected to respective pixels 90. Gate lines 92, whichextend parallel to the rows, and signal lines 94, which extend parallelto the columns, are connected to the TFTs 98. The gate lines 92 areconnected to a line scanning driver 100, and the signal lines 94 areconnected to a multiplexer 102. The gate lines 92 are supplied withcontrol signals Von, Voff for turning on and off the TFTs 98 along therows from the line scanning driver 100. The line scanning driver 100includes a plurality of switches SW1 for switching between the gatelines 92, and an address decoder 104 for outputting a selection signalfor selecting one of the switches SW1 at a time. The address decoder 104is supplied with an address signal from the address signal generator 78(see FIG. 6) of the cassette controller 74.

The signal lines 94 are supplied with electric charges stored by thepixels 90 via the TFTs 98, which are arranged in columns. The electriccharges supplied to the signal lines 94 are amplified by amplifiers 106,which are connected respectively to the signal lines 94. The amplifiers106 are connected through respective sample and hold circuits 108 to themultiplexer 102. The multiplexer 102 includes a plurality of switchesSW2 for successively switching between the signal lines 94, and anaddress decoder 110 for outputting a selection signal for selecting oneof the switches SW2 at a time. The address decoder 110 is supplied withan address signal from the address signal generator 78 of the cassettecontroller 74. The multiplexer 102 has an output terminal connected toan A/D converter 112. A radiographic image signal, which is generated bythe multiplexer 102 based on electric charges from the sample and holdcircuits 108, is converted by the A/D converter 112 into a digital imagesignal representing radiographic image information, which is supplied tothe cassette controller 74.

The TFTs 98, which function as switching devices, may be combined withanother image capturing device, such as a CMOS (ComplementaryMetal-Oxide Semiconductor) image sensor or the like. Alternatively, theTFTs 98 may be replaced with a CCD (Charge-Coupled Device) image sensorfor shifting and transferring electric charges with shift pulses, whichcorrespond to gate signals in the TFTs.

As shown in FIG. 7, the control device 24 includes a communication unit122, a control processor 124, a display unit 126 such as a display panelor the like, an operating unit 128 including a keyboard, a mouse, etc.,an exposure switch 130, an order information storage unit 132, adatabase 134, an image capturing condition storage unit 136, an imagememory 138, and a power supply 140.

The communication unit 122 sends signals to and receives signals fromthe communication unit 64 of the radiation output device 20 and thecommunication unit 72 of the radiation detecting device 22 by way ofwireless communications through the antennas 62, 70, 120. The controlprocessor 124 performs a prescribed control process on the radiationoutput device 20 and the radiation detecting device 22. The exposureswitch 130 can be turned on by the doctor 26 in order to start emittingradiation 16 a through 16 g from the radiation sources 18 a through 18g. The order information storage unit 132 stores order informationrequesting capture of a radiographic image of the subject 14. Thedatabase 134 stores various data concerning weighting of doses ofradiation 16 a through 16 g. The image capturing condition storage unit136 stores image capturing conditions under which a region to be imagedof the subject 14 is to be irradiated with radiation 16 a through 16 g.The image memory 138 stores radiographic images transmitted from theradiation detecting device 22 by way of wireless communications. Thepower supply 140 supplies electric power to various components of thecontrol device 24.

The order information is generated by the doctor 26 for a radiologyinformation system (RIS), not shown, which generally managesradiographic images and other information that are handled in theradiological department of the hospital, or for a hospital informationsystem (HIS), not shown, which generally manages medical information inthe hospital. Such order information includes subject information foridentifying the subject 14, including the name, age, gender, etc.,information concerning the radiation output device 20 and the radiationdetecting device 22, which are used to capture radiographic images, andinformation concerning a region to be imaged of the subject 14. Suchimage capturing conditions refer to various conditions under which aregion to be imaged of the subject 14 is irradiated with radiation 16 athrough 16 g, including tube voltages and tube currents of the radiationsources 18 a through 18 g, radiation exposure times of the radiation 16a through 16 g, etc.

Further, if the control device 24 comprises a console placed in theimage capturing chamber of the radiological department, then the console(control device 24) acquires order information from the RIS or the HIS,and stores the acquired order information in the order informationstorage unit 132. If the control device 24 comprises a portableterminal, which is carried to and used at a site outside of thehospital, then (1) the doctor 26 may operate the operating unit 128 atthe site to provisionally register order information in the orderinformation storage unit 132, (2) order information may be acquired fromthe RIS or the HIS and then stored in the order information storage unit132 in the hospital before the control device 24 is carried to the site,or (3) order information may be received from the hospital through awireless link established between the control device 24 at the site andthe hospital after the control device 24 has been carried to the site,and then stored in the order information storage unit 132.

The control processor 124 includes a database retriever 150, an imagecapturing condition setting unit 152, and a control signal generator154.

The database retriever 150 retrieves desired data corresponding to theregion to be imaged of the subject 14 from the database 134. The imagecapturing condition setting unit 152 sets image capturing conditionsbased on the data received by the database retriever 150 and the orderinformation. The control signal generator 154 generates an exposurecontrol signal for starting emission of radiation 16 a through 16 g fromthe radiation sources 18 a through 18 g in a case that the doctor 26turns on the exposure switch 130.

FIGS. 9 and 10 show tables of various data concerning weighting of thedoses of radiation 16 a through 16 g, in the database 134.

FIG. 9 shows a table that stores therein a plurality of regions to beimaged, thicknesses of the respective regions to be imaged, imagecapturing techniques for the respective regions to be imaged, andoptimum radiation doses (optimum radiation dose data) therefor. Theimage capturing techniques refer to information representative oforientations of the regions to be imaged with respect to the radiationdetecting device 22, and directions along which the regions to be imagedare irradiated with radiation 16 a through 16 g. Further, FIG. 9 showsby way of example data representing a chest, as a relatively largeregion to be imaged, data representing a hand, as a relatively smallregion to be imaged, image capturing techniques (a process for capturinga radiographic image of a frontal chest region, and a process forcapturing a radiographic image of the back of the hand), thicknesses ofthe regions to be imaged, and optimum radiation dose data therefor.

FIG. 10 shows a table storing a plurality of regions to be imaged andimage capturing techniques for the respective regions to be imaged, thenumbers of radiation sources housed in the radiation output device 20,the number of radiation sources to be allocated to each of the groups(grouping data) and weighting (weighting data) of doses of radiation forthe respective groups. More specifically, so as to correspond to FIG. 9,FIG. 10 shows, by way of example, data representing a chest and a handin cases of three radiation sources and seven radiation sources.

FIG. 10 shows, by way of example, the table storing weighting data withrespect to three groups (A, B, C). For example, the groups A, B, Ccorrespond respectively to the groups 54, 56, 58.

In a case where three radiation sources are provided, each of the groups54, 56, 58 contains one radiation source. In a case where sevenradiation sources are provided, the group 54 contains two radiationsources, the group 56 contains three radiation sources, and the group 58contains two radiation sources.

Further, in a case where three or more groups are provided, as a matterof course, the number of grouping data and the number of weighting datain the table shown in FIG. 10 increase depending on the number of thegroups. Additionally, in a case where additional weighting is carriedout with respect to the radiation sources included in one of the groups,as a matter of course, the number of weighting data increases dependingon the number of the radiation sources to be weighted.

The database 134 (see FIG. 7) is capable of storing various dataconcerning image capturing processes that can be carried out by theradiographic image capturing system 10A. Data stored in the database 134can be used even if the subject 14 to be imaged is changed, the regionto be imaged of the subject 14 is changed, or a plurality of subjects 14are imaged sequentially.

A region to be imaged of the subject 14, the thickness of the region tobe imaged, and an image capturing technique are manually entered by thedoctor 26 through the operating unit 128, or alternatively may beincluded in the order information of the subject 14. The region to beimaged, the thickness thereof, and the image capturing technique, whichare manually entered by the doctor 26 through the operating unit 128,are stored as part of the order information in the order informationstorage unit 132, whereby the order information is edited.

For capturing a radiographic image of the region to be imaged of thesubject 14 (image capturing technique), which is represented by theorder information, the database retriever 150 performs the followingprocesses:

The database retriever 150 automatically retrieves, from the table shownin FIG. 9, optimum radiation dose data based on the region to be imagedof the subject 14, the thickness thereof, and the image capturingtechnique therefor. The database retriever 150 also automaticallyretrieves optimum grouping data and weighting data based on the regionto be imaged of the subject 14, the image capturing technique therefor,and the number of radiation sources in the radiation output device 20.Then, the database retriever 150 outputs to the image capturingcondition setting unit 152 the retrieved optimum radiation dose data,the retrieved grouping data and the retrieved weighting data, and theorder information, which includes the region to be imaged of the subject14, the thickness thereof, and the image capturing technique therefor,which have been used for retrieval.

If the database retriever 150 retrieves, from the database 134, aplurality of candidates as optimum radiation dose data, grouping dataand weighting data, then the database retriever 150 may display aplurality of candidates and the order information on the display unit126. In this case, if the doctor 26 confirms the contents displayed onthe display unit 126, and operates the operating unit 128 in order toselect data that appears to be optimum for the image capturing withrespect to the subject 14, then the database retriever 150 outputs theselected optimum radiation dose data, the selected grouping data and theselected weighting data, and the order information to the imagecapturing condition setting unit 152.

The image capturing condition setting unit 152 automatically sets imagecapturing conditions for the region to be imaged of the subject 14,based on the order information, optimum radiation dose data, groupingdata and weighting data retrieved by the database retriever 150(selected by the doctor 26), and stores the set image capturingconditions in the image capturing condition storage unit 136.

Incidentally, the image capturing condition setting unit 152 may displaythe order information, the optimum radiation dose data, the groupingdata and the weighting data retrieved by the database retriever 150 onthe display unit 126. In this case, the doctor 26 confirms the contentsdisplayed on the display unit 126, and operates the operating unit 128in order to change details of the optimum radiation dose data, thegrouping data and the weighting data depending on the order information,the state of the subject 14, or the image capturing technique. The imagecapturing condition setting unit 152 sets image capturing conditionsbased on the optimum radiation dose data, the grouping data and theweighting data, which have been changed.

[Operations of First Embodiment]

The radiographic image capturing system 10A according to the firstembodiment is basically constructed as described above. Next, operations(a radiographic image capturing method) of the radiographic imagecapturing system 10A shall be described below with reference to theflowcharts shown in FIG. 11. Together with this explanation ofoperations, as necessary, FIGS. 1 through 10 may also be referred to.

First, in step S1 shown in FIG. 11, the control processor 124 (see FIG.7) of the control device 24 acquires order information from an externalsource, and stores the acquired order information in the orderinformation storage unit 132. If the control device 24 is a consolelocated in the image capturing chamber of a radiological department,then the control device 24 may acquire order information from the RIS orthe HIS. Further, if the control device 24 is a portable terminal thatcan be carried to and used at a site outside of the hospital, then thedoctor 26 at the site (refer to FIGS. 1, 4B through 5B) may operate theoperating unit 128 in order to register order information, or orderinformation may be acquired from the RIS or the HIS in the hospitalbefore the control device 24 is carried to the site. Alternatively,order information may be received from the hospital through a wirelesslink established between the control device 24 at the site and thehospital, after the control device 24 has been carried to the site.

In step S2, the database retriever 150 identifies a region to be imagedof the subject 14, a thickness thereof, and an image capturing techniquetherefor that are required to search the database 134.

If the order information stored in the order information storage unit132 contains a region to be imaged of the subject 14, a thicknessthereof, and an image capturing technique therefor, then the databaseretriever 150 identifies such information as the region to be imaged,the thickness thereof, and the image capturing technique therefor in thepresent image capturing process.

Also, in a case where the doctor 26 operates the operating unit 128 andthen enters the region to be imaged of the subject 14, the thicknessthereof, and the image capturing technique therefor, the databaseretriever 150 can identify the entered region to be imaged of thesubject 14, the entered thickness thereof and the entered imagecapturing technique therefor, as the region to be imaged, the thicknessthereof and the image capturing technique therefor in the present imagecapturing process. Thus, the identified region to be imaged, theidentified thickness thereof along with the identified image capturingtechnique therefor are stored as part of the order information in theorder information storage unit 132, and then the order information inthe order information storage unit 132 is edited.

Next, in step S3, the database retriever 150 automatically retrieves,from the database 134, a region to be imaged, a thickness, and an imagecapturing technique, which correspond to the region to be imaged of thesubject 14, the thickness, and the image capturing technique that havebeen identified in step S2, and also automatically retrieves optimumradiation dose data corresponding to such items of information. Thedatabase retriever 150 further automatically retrieves, from thedatabase 134, grouping data and weighting data corresponding to theregion to be imaged of the subject 14 and the image capturing techniquetherefor that have been identified in step S2. The database retriever150 then outputs to the image capturing condition setting unit 152 theretrieved optimum radiation dose data, the retrieved grouping data andthe retrieved weighting data, together with the order informationincluding the region to be imaged of the subject 14, the thicknessthereof and the image capturing technique therefor, which have been usedfor retrieval, as various data necessary for capturing of theradiographic image (step S4).

Also, in step S3, if the database retriever 150 retrieves a plurality ofcandidates for the optimum radiation dose data, the grouping data andthe weighting data, then the database retriever 150 displays the pluralcandidates and the order information on the display unit 126. The doctor26 confirms the contents displayed on the display unit 126, and operatesthe operating unit 128 in order to select a candidate (data) thatappears to be optimum for the image capturing process with respect tothe subject 14. The database retriever 150 then regards the optimumradiation dose data, the grouping data and the weighting data, which thedoctor 26 has selected from among the plural candidates, and the orderinformation, as various data necessary for capturing of the radiographicimage, and the database retriever 150 outputs the data to the imagecapturing condition setting unit 152 (step S4).

In step S5, the image capturing condition setting unit 152 sets theimage capturing conditions under which the region to be imaged of thesubject 14 is to be irradiated with radiation 16 a through 16 g emittedfrom the radiation sources 18 a through 18 g, based on the enteredoptimum radiation dose data, the entered grouping data, the enteredweighting data, and the order information.

If the region to be imaged of the subject 14 is a chest, as shown inFIG. 5A, then the image capturing condition setting unit 152 sets theimage capturing conditions (tube voltages, tube currents, andirradiation times) according to the contents of the above data, suchthat the doses of radiation 16 a, 16 b, 16 f, 16 g emitted from theradiation sources 18 a, 18 b, 18 f, 18 g of the side groups 54, 58 areof a maximum dose level, and the doses of radiation 16 c through 16 eemitted from the radiation sources 18 c through 18 e of the centralgroup 56 are of a lower dose level, sufficient to supplement the maximumdose level, and stores the set image capturing conditions in the imagecapturing condition storage unit 136.

Further, if the region to be imaged of the subject 14 is a hand (righthand), as shown in FIG. 5B, then the image capturing condition settingunit 152 sets the image capturing conditions (tube voltages, tubecurrents, and irradiation times) according to the above data, such thatthe doses of radiation 16 c through 16 e emitted from the radiationsources 18 c through 18 e of the central group 56 are of a maximum doselevel, and the doses of radiation 16 a, 16 b, 16 f, 16 g emitted fromthe radiation sources 18 a, 18 b, 18 f, 18 g of the side groups 54, 58are of a lower dose level, sufficient to supplement the maximum doselevel, and stores the set image capturing conditions in the imagecapturing condition storage unit 136.

In step S5, the image capturing condition setting unit 152 may displaythe entered optimum radiation dose data, the entered grouping data, theentered weighting data, and the order information on the display unit126. In this case, the doctor 26 may then confirm the contents displayedon the display unit 126, and by operating the operating unit 128, canchange details of the optimum radiation dose data, the grouping data,and the weighting data depending on the order information, the state ofthe subject 14, or the image capturing technique for the subject 14, aswell as setting desired image capturing conditions in accordance withthe contents of such data, which have been changed. In this case, alsothe image capturing condition setting unit 152 stores the set imagecapturing conditions in the image capturing condition storage unit 136.

Incidentally, in step S5, the image capturing condition setting unit 152may carry out additional weighting of the doses of radiation withrespect to the radiation sources included in the groups, such that therespective radiation sources are weighted with different doses, set adesired image capturing conditions in accordance with the additionalweighting, and may store the set image capturing conditions in the imagecapturing condition storage unit 136, in order to achieve more accurateapplication of the radiation 16 a through 16 g.

Next, in step S6, if the doctor 26 turns on the switch 38 of theradiation detecting device 22 (see FIGS. 2A, 2B, and 5A through 6), thenthe battery 76 supplies electric power to various components inside theradiation detecting device 22, thereby activating the radiationdetecting device 22 in its entirety. Owing thereto, the cassettecontroller 74 sends an activation signal, which indicates that theradiation detecting device 22 has been activated in its entirety, via awireless link to the control device 24 (see FIGS. 1 and 7). The battery76 also applies a bias voltage Vb to the respective pixels 90 (see FIG.8) of the radiation detector 60.

Based on receipt of the activation signal via the antenna 120 and thecommunication unit 122, the control processor 124 of the control device24 sends the image capturing conditions, which are stored in the imagecapturing condition storage unit 136, to the radiation detecting device22 by way of wireless communications. The cassette controller 74 recordstherein the image capturing conditions, which are received via theantenna 70 and the communication unit 72.

Incidentally, in the case that the radiation output device 20 and theradiation detecting device 22 are carried to a site, the connectionterminals 39, 43 are held in interfitting engagement with each other,and the connection terminals 41, 45 also are held in interfittingengagement with each other. Therefore, the radiation output device 20 isheld between the holders 35, 37 of the radiation detecting device 22,and the radiation output device 20 and the radiation detecting device 22are integrally combined with each other (see FIG. 2A). At this time, thebattery 76 charges the battery 68 through the connection terminals 39,41, 43, 45.

For positioning the region to be imaged of the subject 14, the doctor 26releases the connection terminals 39, 43 from interfitting engagementwith each other, and also releases the connection terminals 41, 45 frominterfitting engagement with each other. The radiation output device 20is separated from the radiation detecting device 22, whereby theradiation output device 20 and the radiation detecting device 22 becomedisconnected from each other (see FIG. 2B). At this time, the battery 76stops charging the battery 68.

Then, the doctor 26 positions the region to be imaged of the subject 14,such that the central position of the region to be imaged of the subject14 and the central position of the imaging area 36 become aligned witheach other, and the region to be imaged of the subject 14 is includedwithin the imaging area 36 (see FIGS. 3A and 3B). Thereafter, the doctor26 grips the grip 28 and orients the radiation output device 20 towardthe region to be imaged of the subject 14, so that the distance betweenthe radiation output device 20 and the radiation detecting device 22become equal to a distance depending on the SID, whereupon the touchsensor 52 outputs a detection signal to the radiation source controller66. Based on the input of the detection signal, the radiation sourcecontroller 66 controls the battery 68 in order to supply electric powerto various components of the radiation output device 20, therebyactivating the radiation output device 20. Further, the radiation sourcecontroller 66 sends an activation signal, which indicates that theradiation output device 20 has been activated, via a wireless link tothe control device 24.

Based on receipt of the activation signal via the antenna 120 and thecommunication unit 122, the control processor 124 of the control device24 sends the image capturing conditions stored in the image capturingcondition storage unit 136 to the radiation output device 20 by way ofwireless communications. The radiation source controller 66 records theimage capturing conditions, which are received via the antenna 62 andthe communication unit 64.

Provided that the above preparatory actions have been completed, thedoctor 26 grips the grip 28 with one hand and turns on the exposureswitch 130 with the other hand (step S7). The control signal generator154 generates an exposure control signal for starting emission ofradiation 16 a through 16 g from the radiation sources 18 a through 18g, and sends the exposure control signal via a wireless link to theradiation output device 20 and the radiation detecting device 22. Theexposure control signal is a synchronization control signal forcapturing the radiographic image of the region to be imaged of thesubject 14, as a result of synchronizing start of emission of radiation16 a through 16 g from the radiation sources 18 a through 18 g and thedetection and conversion of such radiation 16 a through 16 g into aradiographic image by the radiation detector 60.

Upon receipt of the exposure control signal by the radiation sourcecontroller 66, the radiation source controller 66 controls the radiationsources 18 a through 18 g in order to apply prescribed doses ofradiation 16 a through 16 g to the subject 14 according to the imagecapturing conditions. The radiation sources 18 a through 18 g emitradiation 16 a through 16 g, which is output from the radiation outputdevice 20 and applied to the region to be imaged of the subject 14, fora given exposure time (irradiation time) based on the image capturingconditions (step S8).

In this case, if the region to be imaged of the subject 14 is a chest,as shown in FIGS. 3A and 5A, then the chest is irradiated with largedoses of radiation 16 a, 16 b, 16 f, 16 g from the radiation sources 18a, 18 b, 18 f, 18 g of the side groups 54, 58, whereas the region to beimaged is irradiated with lower (smaller) doses of radiation 16 cthrough 16 e from the radiation sources 18 c through 18 e of the centralgroup 56, sufficient to supplement the large dose level.

Further, if the region to be imaged of the subject 14 is a right hand,as shown in FIGS. 3B and 5B, then the region to be imaged of the subject14 is irradiated with large doses of radiation 16 c through 16 e fromthe radiation sources 18 c through 18 e of the central group 56, whereasthe right hand of the subject 14 is irradiated with lower doses ofradiation 16 a, 16 b, 16 f, 16 g from the radiation sources 18 a, 18 b,18 f, 18 g of the side groups 54, 58, sufficient to supplement the largedose level.

In step S9, after radiation 16 a through 16 g passes through the subject14 and reaches the radiation detector 60 in the radiation detectingdevice 22, if the radiation detector 60 is of an indirect conversiontype, then the scintillator of the radiation detector 60 emits visiblelight having an intensity depending on the intensity of the radiation 16a through 16 g. The pixels 90 of the photoelectric conversion layer 96(see FIG. 8) convert the visible light into electric signals and storethe electric signals as electric charges therein. The electric charges,which are stored in the pixels as representing a radiographic image ofthe subject 14, are read as address signals, which are supplied from theaddress signal generator 78 of the cassette controller 74 to the linescanning driver 100 and the multiplexer 102.

More specifically, in response to the address signal supplied from theaddress signal generator 78, the address decoder 104 of the linescanning driver 100 outputs a selection signal to select one of theswitches SW1, which supplies the control signal Von to the gates of theTFTs 98 connected to the gate line 92 that corresponds to the selectedswitch SW1. In response to the address signal supplied from the addresssignal generator 78, the address decoder 110 of the multiplexer 102outputs a selection signal to successively turn on the switches SW2 toswitch between the signal lines 94, for thereby reading through thesignal lines 94 the electric charges stored in the pixels 90 connectedto the selected gate line 92.

The electric charges of the radiographic image, which are read from thepixels 90 connected to the selected gate line 92, are amplifiedrespectively by the amplifiers 106, sampled by the sample and holdcircuits 108, supplied to the A/D converter 112 via the multiplexer 102,and converted into digital signals. The digital signals, which representthe first radiographic image, are stored in the image memory 80 of thecassette controller 74 (step S10).

Similarly, the address decoder 104 of the line scanning driver 100successively turns on the switches SW1 to switch between the gate lines92, according to the address signals supplied from the address signalgenerator 78. The electric charges stored in the pixels 90 connected tothe successively selected gate lines 92 are read through the signallines 94, processed by the multiplexer 102, and converted into digitalsignals by the A/D converter 112. The digital signals are stored in theimage memory 80 of the cassette controller 74 (step S10).

The radiographic image, which is stored in the image memory 80, and thecassette ID information, which is stored in the cassette ID memory 82,are sent to the control device 24 wirelessly via the communication unit72 and the antenna 70. The control processor 124 of the control device24 stores the radiographic image and the cassette ID information, whichare received via the antenna 120 and the communication unit 122, in theimage memory 138, and displays the radiographic image on the displayunit 126 (step S11).

After having confirmed that a radiographic image has been obtained byvisually checking the contents displayed on the display unit 126, thedoctor 26 releases the subject 14 from the positioned condition, andremoves the hand from the grip 28. Owing thereto, the touch sensor 52stops outputting the detection signal, and the radiation sourcecontroller 66 stops supplying electric power from the battery 68 to thevarious components of the radiation output device 20. As a result, theradiation output device 20 is brought into a sleep mode or is shut down.Further, if the doctor 26 presses (turns off) the switch 38, then thebattery 76 stops supplying electric power to the various components ofthe radiation detecting device 22, and the radiation detection device 22is brought into a sleep mode or is shut down.

Then, the doctor 26 brings the connection terminals 39, 43 intointerfitting engagement with each other, and also brings the connectionterminals 41, 45 into interfitting engagement with each other, therebyholding the radiation output device 20 between the holders 35, 37, so asto integrally combine the radiation output device 20 and the radiationdetecting device 22 with each other (see FIG. 2A).

[Advantages of First Embodiment]

As described above, according to the radiographic image capturing system10A and the radiographic image capturing method of the first embodiment,at least three radiation sources (seven radiation sources 18 a through18 g in FIGS. 4A through 5B) housed in the radiation output device 20are grouped into at least three groups (three groups 54, 56, 58 in FIGS.5A and 5B).

As shown in FIG. 5A, in a case where the subject 14 is disposed betweenthe radiation output device 20 and the radiation detecting device 22,and a relatively large region to be imaged (e.g., the chest of thesubject 14) is positioned so as to face the geometric center position(the position of the radiation source 18 d) of the radiation sources,according to the first embodiment, weighting of the doses of radiation(radiation 16 a through 16 g) emitted from the respective radiationsources is carried out with respect to the groups, such that the dosesof radiation emitted from the radiation sources included in the groups(groups 54, 58), which are positioned at both sides of the geometriccenter position of the radiation sources, are of a maximum dose level,whereas the doses of radiation emitted from the radiation sourcesincluded in the group (group 56), which is positioned near the geometriccenter position, are of a lower dose level.

On the other hand, as shown in FIG. 5B, in a case where the subject 14is disposed between the radiation output device 20 and the radiationdetecting device 22, and a relatively small region to be imaged (e.g., ahand of the subject 14) is positioned so as to face the geometric centerposition of the radiation sources, according to the first embodiment,weighting of the doses of radiation (radiation 16 a through 16 g)emitted from the respective radiation sources is carried out withrespect to the groups, such that the doses of radiation emitted from theradiation sources included in the group (group 56), which is positionednear the geometric center position, are of a maximum dose level, whereasthe doses of radiation emitted from the radiation sources included inthe groups (groups 54, 58) other than the group positioned near thegeometric center position, are of a lower dose level.

In this manner, according to the first embodiment, an irradiation rangeof the radiation is not established simply by enabling a region to beimaged of the subject 14 to be covered, but rather, the radiationsources are grouped into at least three groups, and radiation doses ofradiation emitted from the respective radiation sources are weightedwith respect to the groups. Thus, even if a radiographic image of thesubject 14 is captured at a short SID using field-emission radiationsources, the irradiation range of radiation can easily be enlarged, andthe subject 14 can be irradiated with an optimum dose (exposure dose) ofradiation. Therefore, according to the first embodiment, by irradiatingthe subject 14 with an optimum dose of radiation depending on thesubject 14, it is possible to acquire a radiographic image suitable fordiagnostic interpretation by the doctor 26, while also preventing thesubject 14 from being exposed to radiation unnecessarily.

In FIG. 5A, the doses of radiation 16 a, 16 b, 16 f, 16 g emitted fromthe radiation sources 18 a, 18 b, 18 f, 18 g belonging to the groups 54,58, which are positioned at both sides of the geometric center position,are of a maximum dose level, whereas the doses of radiation 16 c through16 e emitted from the radiation sources 18 c through 18 e belonging tothe group 56, which is positioned near the geometric center position,are of a lower dose level. Accordingly, it is possible to efficientlycapture a radiographic image of a relatively large region to be imaged.In FIG. 5B, the doses of radiation 16 c through 16 e emitted from theradiation sources 18 c through 18 e belonging to the group 56, which ispositioned near the geometric center position, are of a maximum doselevel, whereas the doses of radiation 16 a, 16 b, 16 f, 16 g emittedfrom the radiation sources 18 a, 18 b, 18 f, 18 g belonging to thegroups 54, 58 other than the group 56, are of a lower dose level.Accordingly, it is possible to efficiently capture a radiographic imageof a relatively small region to be imaged.

Further, the database retriever 150 retrieves, from the database 134,optimum radiation dose data depending on the region to be imaged of thesubject 14, the thickness thereof, and the image capturing techniquetherefor, and together therewith, retrieves grouping data and weightingdata depending on the region to be imaged of the subject 14, thethickness thereof and the image capturing technique therefor.Thereafter, the database retriever 150 outputs the retrieved optimumradiation dose data, the retrieved grouping data, the retrievedweighting data, and the order information to the image capturingcondition setting unit 152. The image capturing condition setting unit152 is thus capable of setting the image capturing conditions accuratelyand efficiently. As a result, by causing the radiation output device 20to apply radiation 16 a through 16 g from the respective radiationsources 18 a through 18 g to the region to be imaged of the subject 14according to the image capturing conditions, capturing of a radiographicimage can be performed at an optimum exposure dose with respect to theregion to be imaged of the subject 14.

The image capturing condition setting unit 152 may change details of theoptimum dose data, the grouping data and the weighting data retrieved bythe database retriever 150, depending on the order information, thestate of the subject 14, or the image capturing technique for thesubject 14. Thus, more accurate image capturing conditions can be setdepending on the actual image capturing technique for the subject 14.

Further, in a case where there is a group including at least tworadiation sources, additional weighting may be carried out with respectto the radiation sources included in the group. As a result, it ispossible to apply radiation to the subject 14 at an optimum dose moreaccurately.

The grip 28 is mounted on the side of the radiation output device 20,which is remote from the side where radiation 16 a through 16 g isemitted from the radiation sources 18 a through 18 g. Consequently,while holding the grip 28 with one hand, the doctor 26 can orient theradiation output device 20 toward the subject 14 and the radiationdetecting device 22. Further, the doctor 26 can confirm images and datadisplayed on the display unit 126, and operate the operating unit 128 orthe exposure switch 130 with the other hand. In a case where radiation16 a through 16 g is emitted from the radiation sources 18 a through 18g while the doctor 26 grips the grip 28, the doctor 26 is reliablyprevented from being irradiated with (exposed to) radiation 16 a through16 g.

Further, in the case that the doctor 26 brings the connection terminals39, 43 and the connection terminals 41, 45 respectively intointerfitting engagement with each other, thereby holding the radiationoutput device 20 between the holders 35, 37 and integrally combining theradiation output device 20 and the radiation detecting device 22 witheach other, the doctor 26 can easily carry the radiation output device20 and the radiation detecting device 22 together. At this time, sincethe connection terminals 39, 43 and the connection terminals 41, 45 areelectrically connected respectively to each other, the battery 76 of theradiation detecting device 22 can charge the battery 68 of the radiationoutput device 20.

Still further, while the radiation output device 20 and the radiationdetecting device 22 are integrally combined with each other, theradiation source controller 66 can prohibit the battery 68 fromsupplying electric power to the radiation sources 18 a through 18 g, forthereby preventing radiation 16 a through 16 g from being emitted whilethe radiation output device 20 and the radiation detecting device 22 arebeing carried. Also, since the side of the radiation output device 20where radiation 16 a through 16 g is emitted from the radiation sources18 a through 18 g faces toward the side of the housing 30 of theradiation detecting device 22 while the radiation output device 20 andthe radiation detecting device 22 are integrally combined with eachother, the doctor 26 is reliably prevented from being exposed toradiation 16 a through 16 g, even if such radiation 16 a through 16 g isemitted in error.

The control device 24 sends signals to and receives signals from theradiation output device 20 and the radiation detecting device 22 via awireless link. Inasmuch as the radiation output device 20, the radiationdetecting device 22, and the control device 24 are connected wirelesslyvia the same wireless link, and since no cables (USB cables) arerequired for signals to be sent and received therebetween, the doctor 26can carry out work free of obstacles. Therefore, the doctor 26 canefficiently work on the radiographic image capturing system 10A in anobstacle-free environment. In addition, the radiographic image capturingsystem 10A is made up of a relatively small number of parts, since nocables are required for connection between the radiation output device20, the radiation detecting device 22, and the control device 24.According to the first embodiment, signals may be sent and received viaoptical wireless communications using infrared rays or the like, ratherthan by means of conventional wireless communications.

According to the first embodiment, the control device 24 can also sendsignals to and receives signals from the radiation output device 20 andthe radiation detecting device 22 via a wired link. For example, theradiation output device 20, the radiation detecting device 22, and thecontrol device 24 may be electrically connected by USB cables (notshown), so that the power supply 140 of the control device 24 can chargethe battery 68 of the radiation output device 20 and the battery 76 ofthe radiation detecting device 22. Further, the control device 24 canreliably send exposure control signals and image capturing conditions tothe radiation output device 20 and the radiation detecting device 22,and the radiation detecting device 22 can reliably send radiographicimages to the control device 24. Accordingly, such a wired link enablessignals to be sent and received reliably, and also allows the batteries68, 76 to be charged reliably.

The batteries 68, 76 may be charged to a power level, which depends onat least the number of radiographic images to be captured of the subject14. Consequently, during the radiographic image capturing process, anumber of radiographic images of the subject 14 can reliably becaptured.

In this case, the batteries 68, 76 may be charged within a time zone inwhich radiographic image capturing process is not being carried out. Inthis manner, the batteries 68, 76 are not charged during theradiographic image capturing process, and the captured radiographicimages are transmitted after completion of the radiographic imagecapturing process. Therefore, during the radiographic image capturingprocess, noise due to charging of the batteries 68, 76 is prevented frombeing added to the generated electric charges (analog signals), or frombeing added to radiographic images while the radiographic images arebeing transmitted.

More specifically, the batteries 68, 76 may be charged within a timezone, except for a period (storage period) during which radiation 16 athrough 16 g having passed through the subject 14 is converted intoelectric signals by the radiation detector 60 and the electric signalsare stored as electric charges in the pixels 90, a period (readoutperiod) during which the electric charges stored in the pixels 90 areread, or a conversion period during which the read electric charges(analog signals) are converted into digital signals by the A/D converter112, or a period covering two or more of the aforementioned storage,readout, and conversion periods, or a period covering all of thestorage, readout, and conversion periods.

More specifically, in the above three periods, i.e., in the storage,readout, and conversion periods, the image signals (radiographic image)are highly susceptible to noise. Particularly during the storage andreadout periods, the electric charges generated by the pixels 90 are sosmall that they will be adversely affected by noise. Further, during theconversion period, the analog signals representing the electric chargesare less resistant to noise than digital signals prior to A/D conversionthereof, and any noise added to the analog signals tends to be convertedinto digital signals and appear in the image data.

A portion of the storage period includes a time during which theradiation sources 18 a through 18 g apply radiation 16 a through 16 g tothe subject 14. After the storage period has started, radiation shouldstart being applied as quickly as possible, and after radiation hasstopped being applied, the readout period should start immediatelythereafter. Any time lag between these events should be minimized, so asto reduce dark current and to increase the quality of the generatedradiographic image. Further, the readout period is a period during whichthe TFTs 98 are turned on to supply signals through the amplifiers 106,etc., and to the A/D converter 112. Although the readout period and theconversion period occur substantially at the same time, the readoutperiod actually starts slightly earlier than the conversion period.

Since the batteries 68, 76 are prohibited from being charged while aradiographic image of the subject 14 is being captured and transmitted,the radiation detector 60 can detect radiation 16 a through 16 gaccurately and with high quality.

The amount of electric power supplied to the batteries 68, 76 within atime zone during which the radiographic image capturing process is notcarried out may be predicted as described below. The batteries 68, 76may be charged with a predicted amount of electric power, in order toallow (a required number of) radiographic images to be capturedreliably.

More specifically, amounts of electric power that are consumed by theradiation output device 20 and the radiation detecting device 22 arecalculated from charging conditions for the batteries 68, 76, and fromprevious and present image capturing conditions (the numbers of capturedradiographic images, mAs values, etc.). Amounts of electric power thatare consumed by the radiation output device 20 and the radiationdetecting device 22 in the present image capturing process, or amountsof electric power that are consumed by the radiation output device 20and the radiation detecting device 22 in the previous image capturingprocess are predicted from the calculated amounts of electric power.

By charging the batteries 68, 76 to respective power levels, which arecommensurate with amounts of electric power expected to be consumedduring the present image capturing process, or with amounts of electricpower consumed during the previous image capturing process, the presentimage capturing process can reliably be carried out.

Further, if the batteries 68, 76 are to be charged during intervalsbetween a plurality of radiographic image capturing events, then theamounts of electric power to be consumed by the radiation output device20 and the radiation detecting device 22 are calculated from chargingconditions and image capturing conditions for radiographic images to becaptured at the present time, from among the present image capturingconditions (numbers of captured radiographic images, mAs values, etc.),except for radiographic images that have already been captured, andamounts of electric power to be consumed for radiographic images to becaptured at the present time are predicted based on the calculated imagecapturing conditions.

In this case as well, since the batteries 68, 76 are charged to a powerlevel commensurate with the amounts of electric power to be consumed forradiographic images to be captured at the present time, any remainingradiographic images to be captured can reliably be captured.

Moreover, in the first embodiment, explanations have been made in whichsignals are sent and received by way of wireless communications and/orwired communications. However, if the subject 14 is held in contact withthe radiation output device 20 and the radiation detecting device 22 ata short SID, then signals may be sent and received between the radiationoutput device 20 and the radiation detecting device 22 by way of humanbody communications via the subject 14. Further, if the doctor 26 isheld in contact with both the radiation output device 20 and the controldevice 24, then signals may be sent and received between the radiationoutput device 20 and the control device 24 by way of human bodycommunications via the doctor 26.

In the first embodiment, the control signal generator 154 generates anexposure control signal for synchronizing emission of radiation 16 athrough 16 g from the radiation sources 18 a through 18 g and conversionof such radiation 16 a through 16 g into a radiographic image by theradiation detector 60, and the communication unit 122 sends the exposurecontrol signal to the radiation output device 20 and the radiationdetecting device 22. Therefore, the radiation sources 18 a through 18 gand the radiation detector 60 can reliably be synchronized with eachother during the radiographic image capturing process.

Further, in the first embodiment, the radiation detecting device 22includes the rectangular housing 30. However, the radiation detectingdevice 22 may be in the form of a flexible sheet including at least theradiation detector 60. Since such a flexible sheet is capable of beingwound into a roll, the radiation detecting device 22 in the form of aflexible sheet can be made compact.

Furthermore, the first embodiment is applicable to acquisition ofradiographic images using a light-readout-type radiation detector. Sucha light-readout-type radiation detector operates as follows. Ifradiation is applied to a matrix of solid-state detecting devices, thenthe solid-state detecting devices store an electrostatic latent image,which is dependent on the dose of applied radiation. For reading thestored electrostatic latent image, reading light is applied to thesolid-state detecting devices in order to cause the solid-statedetecting devices to generate an electric current representing radiationimage information. If erasing light is applied to the radiationdetector, then radiographic image information representing a residualelectrostatic latent image is erased from the radiation detector,whereby the radiation detector can be reused (see Japanese Laid-OpenPatent Publication No. 2000-105297).

Still further, in order to prevent the radiographic image capturingsystem 10A from being contaminated with blood and bacteria, theradiation output device 20 and the radiation detecting device 22 mayhave a water-resistant and hermetically sealed structure, and may besterilized and cleaned as necessary so that the radiographic imagecapturing system 10A can be used repeatedly.

The first embodiment is not limited to capturing of radiographic imagesin the art of medicine, but also may be applied to the capture ofradiographic images in various nondestructive tests.

[Modifications of First Embodiment]

Modifications (first through sixth modifications) of the firstembodiment will be described below with reference to FIGS. 12A through18B.

Parts of such modifications, which are identical to those shown in FIGS.1 through 11, are denoted by identical reference characters, and suchfeatures will not be described in detail below.

[First Modification]

In the first modification, as shown in FIGS. 12A and 12B, each of threegroups 54, 56, 58 contains one radiation source 18 a through 18 c. Inthis case, the geometric center position in the three radiation sources18 a through 18 c is the position of the central radiation source 18 b.The central group 56 includes the geometric center position, whereas theother groups 54, 58 are positioned at both sides of the geometric centerposition.

According to the first modification, in an image capturing process withrespect to a chest region as shown in FIG. 12A, weighting of the dosesis carried out such that the doses of radiation 16 a, 16 c emitted fromthe radiation sources 18 a, 18 c included in the groups 54, 58 are of amaximum dose level, whereas the dose of radiation 16 b emitted from theradiation source 18 b included in the group 56 is of a lower dose level.On the other hand, in an image capturing process with respect to a handas shown in FIG. 12B, weighting of the doses is carried out such thatthe dose of radiation 16 b emitted from the radiation source 18 bincluded in the group 56 is of a maximum dose level, whereas the dosesof radiation 16 a, 16 c emitted from the radiation sources 18 a, 18 cincluded in the groups 54, 58 are of a lower dose level.

Even in the first modification in which each of the three groups 54, 56,58 contains only one radiation source 18 a through 18 c, it is a matterof course that, by carrying out such weighting, the same advantages asthose of the first embodiment can be obtained.

[Second Modification]

In the second modification, as shown in FIGS. 13A and 13B, each of fourgroups 156, 158, 160, 162 contains one radiation source 18 a through 18d. In this case, the geometric center position in the four radiationsources 18 a through 18 d is an intermediate position between theradiation source 18 b and the radiation source 18 c. The groups 158, 160including the radiation sources 18 b, 18 c do not include the geometriccenter position but are positioned near the geometric center position,whereas the other groups 156, 162 are positioned at both sides of thegeometric center position.

According to the second modification, in an image capturing process withrespect to a chest region as shown in FIG. 13A, weighting of the dosesis carried out such that the doses of radiation 16 a, 16 d emitted fromthe radiation sources 18 a, 18 d included in the groups 156, 162 are ofa maximum dose level whereas the doses of radiation 16 b, 16 c emittedfrom the radiation sources 18 b, 18 c included in the groups 158, 160are of a lower dose level. On the other hand, in an image capturingprocess with respect to a hand as shown in FIG. 13B, weighting of thedoses is carried out such that the doses of radiation 16 b, 16 c emittedfrom the radiation sources 18 b, 18 c included in the groups 158, 160are of a maximum dose level whereas the doses of radiation 16 a, 16 demitted from the radiation sources 18 a, 18 d included in the groups156, 162 are of a lower dose level.

Even in the second modification in which each of the four groups 156,158, 160, 162 contains only one radiation source 18 a through 18 d, itis a matter of course that, by carrying out such weighting, the sameadvantages as those of the first embodiment can be obtained.

As described above, in the first embodiment and first modification,explanation has been made, by way of example, on the case that weightingof the doses is carried out with respect to the three groups 54 though58. However, also in a case that the number of the groups is an oddnumber (3, 5, 7, . . . ) which is equal to or greater than three, ifweighting is carried out based on the principle of the first embodimentand first modification, then the same advantages as those of the firstembodiment and first modification can be obtained easily. Further, inthe second modification, explanation has been made, by way of example,on the case that weighting of the doses is carried out with respect tothe four groups 156, 158, 160, 162. However, also in a case that thenumber of the groups is an even number (4, 6, 8, . . . ) which is equalto or greater than four, if weighting is carried out based on theprinciple of the second modification, then the same advantages as thoseof the second modification (and the first embodiment) can be obtainedeasily.

[Third Modification]

According to a third modification, as shown in FIGS. 14A and 14B, acasing 46 of the radiation output device 20 includes a recess 164defined in a side thereof remote from the side at which radiation 16 athrough 16 g is emitted from the radiation sources 18 a through 18 g. Acollapsible grip 166 is pivotally movably disposed for storage in therecess 164. A touch sensor 52 is incorporated in the grip 166.

In the case that the doctor 26 is not carrying the radiation outputdevice 20, the grip 166 is accommodated flatwise in the recess 164, asshown in FIG. 14A. If the doctor 26 turns the grip 166 about the pivotedend, then the grip 166 is raised out from the recess 164, so that thedoctor 26 can grip the grip 166 (see FIG. 14B). The grip 166 and thetouch sensor 52 offer the same advantages as those of the grip 28 andthe touch sensor 52 according to the first embodiment. Further, in acase where the grip 166 is turned about the pivoted end back into therecess 164, the grip 166 is placed flatwise in the recess 164, therebykeeping the electrodes of the touch sensor 52 out of contact with thehand of the doctor 26. Therefore, the radiation output device 20 isprevented from being activated, and hence the radiation sources 18 athrough 18 g are prevented from emitting radiation 16 a through 16 g inerror.

[Fourth Modification]

According to a fourth modification, as shown in FIGS. 15A and 15B, thecasing 46 of the radiation output device 20 is of a rectangular shape,the planar area of which is substantially the same as the radiationdetecting device 22. The casing 46 houses therein nine radiation sources18 a through 18 i. The casing 46 is not required to house all nine ofthe radiation sources 18 a through 18 i, but may house at least threeradiation sources.

The radiation sources 18 a through 18 i are arranged in atwo-dimensional matrix facing toward the irradiated surface 32, whichdiffers from the above-described linear array of radiation sources 18 athrough 18 g that face toward the irradiated surface 32 (see FIGS. 1,5A, 5B and 12A through 13B).

Further, the casing 46 has a grip 28 disposed on an upper surfacethereof, and also has unlocking buttons 167 on opposite side surfacesthereof for releasing hooks 165, which are mounted on the bottom surfaceof the casing 46, from openings 163 that are defined respectively infour corners on the upper surface of the housing 30 of the radiationdetecting device 22.

Furthermore, the housing 30 has connection terminals 173, 175 disposedon the upper surface thereof outside of the imaging area 36, which serveas jacks, which are capable of interfitting engagement with respectivepin-shaped connection terminals 169, 171 mounted on the bottom surfaceof the casing 46.

In the condition shown in FIG. 15A, the hooks 165 engage respectively inthe openings 163, and the connection terminals 169, 171 are held ininterfitting engagement respectively with the connection terminals 173,175, thereby holding the radiation output device 20 and the radiationdetecting device 22 integrally with each other. Owing thereto, thedoctor 26 can grip the grip 28, or insert his or her hand between thegrip 28 and the upper surface of the casing 46, in order to carry theradiation output device 20 and the radiation detecting device 22, whichare integrally combined with each other. Further, in such an integratedcondition, the battery 76 of the radiation detecting device 22 (see FIG.6) is capable of charging the battery 68 of the radiation output device20 via the connection terminals 169, 171, 173, 175.

On the other hand, if the doctor 26 presses the unlocking buttons 167 inorder to release the hooks 165 from the respective openings 163, andgrips the grip 28 or inserts his or her hand between the grip 28 and theupper surface of the casing 46 so as to separate (lift) the radiationoutput device 20 from the radiation detecting device 22, then theconnection terminals 169, 171 are released from the connection terminals173, 175, whereby the integrated state between the radiation outputdevice 20 and the radiation detecting device 22 is released. As a resultthereof, the battery 76 stops charging the battery 68, and the radiationsources 18 a through 18 i are made capable of emitting radiationrespectively.

According to the fourth modification, since the radiation sources 18 athrough 18 i are arranged in a two-dimensional matrix, radiographicimages of any regions to be imaged of the subject 14 can be capturedefficiently. Further, as the casing 46 of the radiation output device 20is essentially of the same rectangular shape as the housing 30 of theradiation detecting device 22, the radiation output device 20 and theradiation detecting device 22, which are integrally combined with eachother, are rendered highly portable, and the radiation output device 20can easily be positioned with respect to the radiation detecting device22.

The fourth modification thus offers the same advantages as those of thefirst embodiment, as well as the first through third modifications.

[Fifth Modification]

In the above explanation, the photoelectric conversion layer 96, whichserves as one of the components of the radiation detector 60, is made ofamorphous silicon (a-Si) or the like. However, according to the firstembodiment, the photoelectric conversion layer may include an organicphotoelectric conversion material.

A radiation detector including a photoelectric conversion layer, whichincludes an organic photoelectric conversion material according to afifth modification, will be described below with reference to FIGS. 16and 17.

As shown in FIG. 16, a radiation detector 170 includes a signal outputsection 174, a sensor 176, and a scintillator 178, which aresuccessively deposited on an insulating substrate 172. The signal outputsection 174 and the sensor 176 jointly make up a pixel. The radiationdetector 170 includes a matrix of pixels arrayed on the substrate 172.In each of the pixels, the signal output section 174 is superposed onthe sensor 176.

More specifically, the radiation detector 170 shown in FIGS. 16 and 17is a rear surface reading type, i.e., a penetration side sample (PSS)type, of radiation detector, in which the scintillator 178, the sensor176 and the signal output section 174 are arranged in this order alongthe direction in which radiation 16 a through 16 c is applied.Explanations concerning a front surface reading type, i.e., anirradiation side sampling (ISS) type, of radiation detector, in whichthe signal output section 174, the sensor 176 and the scintillator 178are arranged in this order along the direction in which radiation 16 athrough 16 g is applied, shall be given subsequently.

The scintillator 178 is disposed over the sensor 176 with a transparentinsulating film 180 interposed therebetween. The scintillator 178 is inthe form of a film made of phosphor, for emitting light converted fromradiation 16 a through 16 g (see FIGS. 1, 4B, 5A through 6, and 12Athrough 14B) that is applied from above, at a location remote from thesubstrate 172. The scintillator 178 can absorb radiation 16 a through 16g that has passed through the subject 14 and emit light convertedtherefrom.

Light emitted by the scintillator 178 should preferably have a visiblewavelength range from 360 nm to 830 nm. If the radiation detector 170 isused to capture a monochromatic image, then light emitted by thescintillator 178 should preferably include a green wavelength range.

If X-rays are used as the radiation 16 a through 16 g, then the phosphorused in the scintillator 178 should preferably include cesium iodide(CsI), and particularly preferably, should include CsI(Tl)(thallium-added cesium iodide) which, when irradiated with X-rays, emitslight in a wavelength spectrum ranging from 420 nm to 700 nm. Lightemitted from CsI(Tl) has a peak wavelength of 565 nm in the visiblerange. Further, such a phosphor is not limited to CsI(Tl), and othermaterials such as CsI(Na) (sodium-activated cesium iodide) or GOS(Gd₂O₂S:Tb) may also be used.

The sensor 176 includes an upper electrode 182, a lower electrode 184,and a photoelectric conversion film 186 disposed between the upperelectrode 182 and the lower electrode 184. The photoelectric conversionfilm 186 is made of an organic photoelectric conversion material forgenerating electric charges by absorbing light emitted by thescintillator 178.

Since the light emitted by the scintillator 178 must be applied to thephotoelectric conversion film 186, the upper electrode 182 shouldpreferably be made of an electrically conductive material, which istransparent to at least the wavelength of the light emitted by thescintillator 178. More specifically, the upper electrode 182 shouldpreferably be made of a transparent conducting oxide (TCO), which is ofa high transmittance with respect to visible light and has a smallresistance value. Although the upper electrode 182 may be made of a thinmetal film such as of Au or the like, TCO is preferable thereto becauseAu tends to have an increased resistance value at transmittances of 90%or higher. For example, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide),AZO (Aluminum doped Zinc Oxide), FTO (Fluorine doped Tin Oxide), SnO₂,TiO₂, ZnO₂, or the like should preferably be used as the material of theupper electrode 182. Among these materials, ITO is the most preferablefrom the standpoints of process simplification, low resistance, andtransparency. The upper electrode 182 may be a single electrode sharedby all of the pixels, or may be a plurality of electrodes assigned torespective pixels.

The photoelectric conversion film 186 may be made of a material thatabsorbs visible light and generates electrical charges, and may utilizethe aforementioned amorphous silicon (a-Si) or an organic photoelectricconversion (OPC) material, which absorbs light emitted by thescintillator 178 and generates electric charges depending on theabsorbed light.

In the case that the photoelectric conversion film 186 is constituted byamorphous silicon, a structure can be provided so as to absorb over awide wavelength range visible light that is emitted from thescintillator 178. However, vapor deposition must be carried out in orderto form the photoelectric conversion film 186 from amorphous silicon,and in the event that the substrate 172 is a synthetic resin, specialconsideration must be given to heat resistance of the substrate 172.

On the other hand, in the case that a photoelectric conversion film 186including an organic photoelectric conversion material is used, thephotoelectric conversion film 186 has a sharp absorption spectrum in thevisible range and does not absorb electromagnetic waves other than lightemitted by the scintillator 178. Therefore, any noise, which would beproduced if radiation 16 a through 16 g such as X-rays were absorbed bythe photoelectric conversion film 186, is effectively minimized.

Further, since a photoelectric conversion film 186 made from an organicphotoelectric conversion material can be formed using a liquid dropletdischarge head such as an inkjet head or the like, in which the organicphotoelectric conversion material is made to adhere to a formed body, itis not necessary that the formed body be resistant to heat.

In order for the organic photoelectric conversion material of thephotoelectric conversion film 186 to absorb light emitted by thescintillator 178 most efficiently, the absorption peak wavelengththereof should preferably be as close as possible to the light emissionpeak wavelength of the scintillator 178. Although the absorption peakwavelength of the organic photoelectric conversion material and thelight emission peak wavelength of the scintillator 178 should ideally bein agreement with each other, it is possible to sufficiently absorblight emitted by the scintillator 178 if the difference between theabsorption peak wavelength and the light emission peak wavelength issufficiently small. More specifically, the difference between theabsorption peak wavelength of the organic photoelectric conversionmaterial and the light emission peak wavelength of the scintillator 178with respect to the radiation 16 a through 16 g should preferably be 10nm or smaller, and more preferably, 5 nm or smaller.

Organic photoelectric conversion materials that meet the aboverequirements include quinacridone-based organic compounds andphthalocyanine-based organic compounds. Since quinacridone has anabsorption peak wavelength of 560 nm in the visible range, ifquinacridone is used as the organic photoelectric conversion materialand CsI(Tl) as the material of the scintillator 178, the differencebetween the above peak wavelengths can be reduced to 5 nm or smaller,thus making it possible to substantially maximize the amount of electriccharges generated by the photoelectric conversion film 186.

The photoelectric conversion film 186, which is applicable to theradiation detector 170, will be described in specific detail below.

The radiation detector 170 includes an electromagnetic waveabsorption/photoelectric conversion region, which is provided by anorganic layer including the electrodes 182, 184 and the photoelectricconversion film 186 sandwiched between the electrodes 182, 184. Theorganic layer may be formed by the superposition or mixture of anelectromagnetic wave absorption region, a photoelectric conversionregion, an electron transport region, a hole transport region, anelectron blocking region, a hole blocking region, a crystallizationpreventing region, an electrode, and an interlayer contact improvingregion, etc.

The organic layer should preferably include an organic p-type compoundor an organic n-type compound.

An organic p-type semiconductor (compound) is a donor organic compoundmainly typified by a hole transport organic compound, and refers to anorganic compound that tends to donate electrons. More specifically, in acase where two organic materials are used in contact with each other,one of the organic materials, which has a lower ionization potential, isreferred to as a donor organic compound. Any organic compounds that arecapable of donating electrons can be used as the donor organic compound.

An organic n-type semiconductor (compound) is an acceptor organiccompound mainly typified by an electron transport organic compound, andrefers to an organic compound that tends to accept electrons. Morespecifically, in a case where two organic materials are used in contactwith each other, one of the organic materials, which has a largerelectron affinity, is referred to as an acceptor organic compound. Anyorganic compounds that are capable of accepting electrons can be used asthe acceptor organic compound.

Materials that can be used as the organic p-type semiconductor and theorganic n-type semiconductor, and arrangements of the photoelectricconversion film 186 are disclosed in detail in Japanese Laid-Open PatentPublication No. 2009-032854, and such features will not be described indetail below.

The sensor 176 of each pixel may include at least the lower electrode184, the photoelectric conversion film 186, and the upper electrode 182.For preventing an increase in dark current, the sensor 176 shouldpreferably additionally include either an electron blocking film 188 ora hole blocking film 190, and more preferably, should include both theelectron blocking film 188 and the hole blocking film 190.

The electron blocking film 188 may be disposed between the lowerelectrode 184 and the photoelectric conversion film 186. In a case wherea bias voltage is applied between the lower electrode 184 and the upperelectrode 182, the electron blocking film 188 is capable of preventingelectrons from being injected from the lower electrode 184 into thephotoelectric conversion film 186, thereby preventing dark current fromincreasing.

The electron blocking film 188 may be made of an organic materialcapable of donating electrons.

The electron blocking film 188 is actually made of a material that isselected depending on the material of the lower electrode 184 and thematerial of the photoelectric conversion film 186, which lie adjacentthereto. Preferably, the material should have an electron affinity (Ea)that is at least 1.3 eV greater than the work function (Wf) of thematerial of the adjacent lower electrode 184, and an ionizationpotential (Ip) that is equal to or smaller than the Ip of the materialof the adjacent photoelectric conversion film 186. Materials that can beused as an organic material, and which are capable of donatingelectrons, are disclosed in detail in Japanese Laid-Open PatentPublication No. 2009-032854, and such materials will not be described indetail below.

The thickness of the electron blocking film 188 should preferably be ina range from 10 nm to 200 nm, more preferably in a range from 30 nm to150 nm, and particularly preferably in a range from 50 nm to 100 nm, inorder to reliably achieve a dark current reducing capability, and toprevent the photoelectric conversion efficiency of the sensor 176 frombeing lowered.

The hole blocking film 190 may be disposed between the photoelectricconversion film 186 and the upper electrode 182. In a case where a biasvoltage is applied between the lower electrode 184 and the upperelectrode 182, the hole blocking film 190 is capable of preventing holesfrom being injected from the upper electrode 182 into the photoelectricconversion film 186, thereby preventing dark current from increasing.

The hole blocking film 190 may be made of an organic material, which iscapable of accepting electrons.

The thickness of the hole blocking film 190 should preferably be in arange from 10 nm to 200 nm, more preferably in a range from 30 nm to 150nm, and particularly preferably in a range from 50 nm to 100 nm, inorder to reliably achieve a dark current reducing capability, and toprevent the photoelectric conversion efficiency of the sensor 176 frombeing lowered.

The hole blocking film 190 is actually made of a material that isselected depending on the material of the upper electrode 182 and thematerial of the photoelectric conversion film 186 that lie adjacentthereto. A preferable material should have an ionization potential (Ip)that is at least 1.3 eV greater than the work function (Wf) of thematerial of the adjacent upper electrode 182, and an electron affinity(Ea) equal to or greater than the Ea of the material of the adjacentphotoelectric conversion film 186. Materials that can be used as organicmaterials capable of accepting electrons are disclosed in detail inJapanese Laid-Open Patent Publication No. 2009-032854, and suchmaterials will not be described in detail below.

In order to set a bias voltage to move holes, from among the electriccharges generated in the photoelectric conversion film 186, toward theupper electrode 182, and to move electrons, from among the electriccharges generated in the photoelectric conversion film 186, toward thelower electrode 184, the electron blocking film 188 and the holeblocking film 190 may be switched in position. The electron blockingfilm 188 and the hole blocking film 190 are not both required, butrather, either one of the electron blocking film 188 and the holeblocking film 190 may be included so as to provide a certain darkcurrent reducing capability.

The signal output section 174 is formed on the surface of the substrate172 beneath the lower electrode 184 of each pixel. FIG. 17 schematicallyshows structural details of the signal output section 174.

The signal output section 174 includes a capacitor 192, which is alignedwith the lower electrode 184, for storing electric charges that havemoved to the lower electrode 184, and a field-effect thin filmtransistor (hereinafter also referred to simply as a “thin filmtransistor” or TFT) 194 for converting the electric charges stored inthe capacitor 192 into electric signals, and outputting the electricsignals. The capacitor 192 and the thin film transistor 194 are disposedin a region underlapping the lower electrode 184 as viewed in plan. Thisstructure enables the signal output section 174 and the sensor 176 to besuperposed in each pixel in the thickness direction. In order tominimize the planar area of the radiation detector 170 (pixels), it isdesirable for the region in which the capacitor 192 and the thin filmtransistor 194 are disposed to be fully covered with the lower electrode184.

The capacitor 192 is electrically connected to the lower electrode 184by an electrically conductive interconnection, which extends through aninsulating film 196 interposed between the substrate 172 and the lowerelectrode 184. The interconnection allows electric charges collected bythe lower electrode 184 to migrate toward the capacitor 192.

As shown in FIG. 17, the thin film transistor 194 includes a stackedassembly made up of a gate electrode 198, a gate insulating film 200,and an active layer (channel layer) 202, and a source electrode 204 anda drain electrode 206 disposed on the active layer 202 and spaced fromeach other with a gap therebetween. In the radiation detector 170,although the active layer 202 may be formed by any of amorphous silicon,an amorphous oxide, an organic semiconductor material, carbon nanotubesor the like, materials capable of forming the active layers are notlimited to the foregoing materials.

As an amorphous oxide that constitutes the active layer 202, such anamorphous oxide should preferably be an oxide (e.g., In—O oxide)including at least one of In, Ga, and Zn, more preferably, an oxide(e.g., In—Zn—O oxide, In—Ga—O oxide, or Ga—Zn—O oxide) including atleast two of In, Ga, and Zn, and particularly preferably, an oxideincluding In, Ga, and Zn. An In—Ga-An-O amorphous oxide shouldpreferably be an amorphous oxide, the crystalline composition of whichis represented by InGaO₃ (ZnO)_(m) where m represents a natural numbersmaller than 6, and more particularly, preferably should be InGaZnO₄.However, amorphous oxides capable of forming the active layer 202 arenot limited to the foregoing.

Further, as organic semiconductor materials capable of forming theactive layer 202, for example, there may be used phthalocyaninecompounds, pentacene, vanadyl phthalocyanine or the like, although thepresent invention is not limited to such materials. Concerningphthalocyanine compounds, details thereof are described in detail inJapanese Laid-Open Patent Publication No. 2009-212389, and detailedexplanations of such compounds are omitted.

If the active layer 202 of the thin film transistor 194 is made from anyof an amorphous oxide, an organic semiconductor material, carbonnanotubes or the like, then since the active layer 202 does not absorbradiation 16 a through 16 g such as X-rays or the like, or absorbs onlyan extremely small amount of radiation 16 a through 16 c, the activelayer 202 is effective to reduce noise generated in the signal outputsection 174.

Further, if the active layer 202 is formed from carbon nanotubes, theswitching speed of the thin film transistor 194 can be increased, andabsorption of light in the visible light band in the thin filmtransistor 194 can be lessened. Moreover, if the active layer 202 isformed from carbon nanotubes, because performance of the thin filmtransistor 194 is lowered remarkably as a result of being mixed withonly extremely small amounts of metallic impurities, it is necessary toform the active layer 202 by separating and extracting carbon nanotubes,which are extremely high in purity, by means of centrifugal separationor the like.

Further, because films formed from organic photoelectric conversionmaterials and films formed from organic semiconductor materials possesssufficient flexibility, if a structure is constituted by a combinationof a photoelectric conversion film 186 formed from an organicphotoelectric conversion material and a thin film transistor 194 inwhich the active layer 202 thereof is formed from an organicsemiconductor material, it becomes unnecessary for the TFT substrate 208to have high rigidity to accommodate as a load the weight of the body ofthe subject 14.

The amorphous oxide of the active layer 202 of the thin film transistor194, and the organic photoelectric conversion material of thephotoelectric conversion film 186 can be deposited as films at lowtemperatures. Therefore, the substrate 172 is not limited to a highlyheat-resistant substrate, such as a semiconductor substrate, a quartzsubstrate, a glass substrate, or the like, but may be a flexiblesubstrate made of plastic, a substrate of aramid fibers, or a substrateof bionanofibers. More specifically, the substrate 172 may be a flexiblesubstrate of polyester, such as polyethylene terephthalate, polybutylenephthalate, polyethylene naphthalate, or the like, polystyrene,polycarbonate, polyethersulfone, polyarylate, polyimide,polycycloolefine, norbornene resin, poly(chlorotrifluoro-ethylene), orthe like. A flexible substrate fabricated from plastic makes theradiation detector 170 light in weight and hence easier to carry.

The substrate 172 may include an insulating layer for thereby making thesubstrate 172 electrically insulative, a gas barrier layer for makingthe substrate 172 impermeable to water and oxygen, and an undercoatlayer for making the substrate 172 flat or improving intimate contactbetween the substrate 172 and the electrode.

Aramid fibers for use as the substrate 172 are advantageous in that,since a high-temperature process at 200° C. is applicable thereto,aramid fibers allow a transparent electrode material to be set at a hightemperature for lower resistance, and also allow driver ICs to beautomatically mounted thereon by a process including a solder reflowprocess. Furthermore, since aramid fibers have a coefficient of thermalexpansion that is close to ITO (Indium Tin Oxide) and glass, aninsulating substrate made of aramid fibers is less likely to suffer fromwarpage and cracking after fabrication thereof. In addition, aninsulating substrate made of aramid fibers may be fabricated thinnerthan a glass substrate or the like. The substrate 172 may be in the formof a stacked assembly of an ultrathin glass substrate and aramid fibers.

Bionanofibers are made by compounding a bundle of cellulose microfibrils(bacteria cellulose) produced by bacteria (acetic acid bacteria,Acetobacter xylinum) and a transparent resin. The bundle of cellulosemicrofibrils has a width of 50 nm, which is 1/10 of the wavelength ofvisible light, is highly strong and highly resilient, and is subject tolow thermal expansion. Bionanofibers, which contain 60% to 70% fibersand exhibit a light transmittance of about 90% at a wavelength of 500nm, can be produced by impregnating bacteria cellulose with atransparent resin such as an acrylic resin, an epoxy rein, or the like,and setting the transparent resin. Bionanofibers are flexible, and havea low coefficient of thermal expansion ranging from 3 ppm to 7 ppm,which is comparable to silicon crystals, a high strength of 460 MPa thatmatches the strength of steel, and a high resiliency of 30 GPa.Therefore, an insulating substrate 172, which is made of bionanofibers,can be thinner than glass substrates or the like.

Since the photoelectric conversion film 186 of the radiation detector170 is made of an organic photoelectric conversion material, thephotoelectric conversion film 186 absorbs almost none of the radiation16 a through 16 g. Therefore, in a PSS type of radiation detector 170,even if the radiation 16 a through 16 g passes through a TFT substrate208, since the photoelectric conversion film 186 absorbs only a smallamount of radiation 16 a through 16 g, any reduction in sensitivity tothe radiation 16 a through 16 g is minimized. With a PSS type ofradiation detector 170, radiation 16 a through 16 g passes through theTFT substrate 208 and reaches the scintillator 178. However, since thephotoelectric conversion film 186 of the TFT substrate 208 is made of anorganic photoelectric conversion material, the photoelectric conversionfilm 186 essentially does not absorb radiation 16 a through 16 g, andany attenuation in radiation 16 a through 16 g is minimized. Therefore,a photoelectric conversion film 186, which is made of an organicphotoelectric conversion material, is suitable for use in a PSS typeradiation detector.

The amorphous oxide of the active layer 202 of the thin film transistor194 and the organic photoelectric conversion material of thephotoelectric conversion film 186 can be deposited as films at lowtemperatures. Therefore, the substrate 172 may be made of plastic,aramid fibers, or bionanofibers, which absorb only small amounts ofradiation 16 a through 16 g. Since the substrate 172 thus made ofplastic, aramid fibers, or bionanofibers absorbs only a small amount ofradiation 16 a through 16 g, the substrate 172 is effective to preventsensitivity to radiation 16 a through 16 g from being lowered, even ifradiation 16 a through 16 g passes through the TFT substrate 208 due tobeing used in a PSS type radiation detector.

According to the fifth modification, the radiation detector 170 may beconstituted in the following manner.

(1) The sensor 176 including the photoelectric conversion film 186 madeof an organic photoelectric conversion material may be constructed so asto constitute the signal output section 174 using a CMOS sensor. In thiscase, since only the sensor 176 is made up from an organic photoelectricconversion material, the signal output section 174 including the CMOSsensor does not need to be flexible. Concerning the sensor 176, which isconstructed to include an organic photoelectric conversion material, aswell as the CMOS sensor, details thereof have been described in JapaneseLaid-Open Patent Publication No. 2009-212377, and thus detailedexplanations of such features are omitted.

(2) The sensor 176 including the photoelectric conversion film 186 madeof an organic photoelectric conversion material may be constructed so asto realize the signal output section 174, which possesses flexibility,by a CMOS circuit equipped with a thin film transistor (TFT) 194 made upfrom an organic material. In this case, pentacene may be adopted as amaterial of a p-type organic semiconductor, and fluorinated copperphthalocyanine (F₁₆CuPc) may be adopted as an n-type organicsemiconductor used by the CMOS circuit. In accordance therewith, a TFTsubstrate 208 having a certain flexibility with a smaller radius ofcurvature can be realized. Further, by constructing the TFT substrate208 in this manner, the gate insulating film 200 can be made quite thin,thus enabling the drive voltage to be lowered. Furthermore, the gateinsulating film 200, the semiconductor body, and each of the electrodescan be manufactured at room temperature or at a temperature of 100° C.or less. Still further, the CMOS circuit may be manufactured directly onsuch a flexible insulating substrate 172. Additionally, the thin filmtransistor 194 made from an organic material can be miniaturized by amanufacturing process in accordance with scaling rules. For thesubstrate 172, if a polyimide precursor is coated on a polyimidesubstrate and heated using a spin coat method, because the polyimideprecursor is converted into a polyimide, a flat substrate free ofconcave-convex irregularities can be realized.

(3) A self-assembly technique (fluidic self-assembly method) in which aplurality of micron-order device blocks are arranged in specifiedpositions on a substrate may be applied, and the sensor 176 and thesignal output section 174 may be arranged on an insulating substrate 172made up from a resin substrate. In this case, the sensor 176 and thesignal output section 174, which are micron-order miniature deviceblocks, are manufactured on another substrate and thereafter areseparated from the substrate. Then, the sensor 176 and the signal outputsection 174 are dispersed in a liquid and arranged statistically on thesubstrate 172, which serves as a target substrate. A process may beimplemented on the substrate 172 in advance for adapting the substrate172 to the device blocks, and the device blocks can be selectivelyarranged on the substrate 172. Accordingly, optimum device blocks (i.e.,the sensor 176 and the signal output section 174) made up from optimalmaterials can be integrated on an optimal substrate (insulatingsubstrate 172), and the sensor 176 and the signal output section 174 canbe integrated on a non-crystalline insulating substrate 172 (resinsubstrate).

[Sixth Modification]

Next, as a sixth modification of the present invention, an example of anirradiation side sampling (ISS) type of radiation detector 300 includinga CsI(Tl) scintillator 500 shall be described with reference to FIGS.18A and 18B.

The radiation detector 300 comprises an ISS type radiation detector, inwhich a radiation detecting unit 502, which offers substantially thesame functions as the TFT substrate 208 including the signal outputsection 174 and the sensor 176, and a CsI(Tl) scintillator 500 arearranged in this order with respect to an irradiated surface 32, whichis irradiated with radiation 16 a through 16 g (i.e., along a directionin which radiation 16 a through 16 g is applied).

In the scintillator 500, the irradiated surface 32 side that isirradiated with radiation 16 a through 16 g generates and emits lightmore intensively. In an ISS type of radiation detector, thelight-emitting position in the scintillator 500 is proximate to theradiation detecting unit 502. Thus, compared to a PSS type, an ISS typeof radiation detector has a higher ability to resolve the radiographicimage, which is obtained through image capturing. Further, the emittedamount of visible light by the radiation detecting unit 502 isincreased. Accordingly, more so than a PSS type, an ISS type ofradiation detector can enhance the sensitivity of the radiation detector300 (radiation detecting device 22).

As one example thereof, FIG. 18B shows a case in which a scintillator500 including a columnar crystalline domain is formed by vapordepositing a material including CsI on a vapor deposition substrate 504.

More specifically, in the scintillator 500 of FIG. 18B, a structure isprovided in which a columnar crystalline domain is formed from columnarcrystals 500 a on the side of the irradiated surface 32 (side of theradiation detecting unit 502), which is irradiated with radiation 16 athrough 16 g, and a non-columnar crystalline domain is formed fromnon-columnar crystals 500 b on a side opposite from the irradiatedsurface 32. A material of high heat resistance preferably is used as thevapor deposition substrate 504. For example, from the standpoint oflowering costs, aluminum (Al) is preferable. Further, in thescintillator 500, the average diameter of the columnar crystals 500 a issubstantially uniform over the longitudinal dimension of the columnarcrystals 500 a.

In the above manner, the scintillator 500 is a structure that is formedby a columnar crystalline domain (columnar crystals 500 a) and anon-columnar crystalline domain (non-columnar crystals 500 b), andtogether therewith, the columnar crystalline domain, which is made upfrom columnar crystals 500 a from which light is emitted with highefficiency, are arranged on the side of the radiation detecting unit502. Owing thereto, visible light emitted by the scintillator 500progresses within the columnar crystals 500 a and is irradiated towardthe radiation detecting unit 502. As a result, dispersion of visiblelight, which is irradiated toward the side of the radiation detectingunit 502, is suppressed, and blurring of the radiographic image, whichis detected by the radiation detecting device 22, also is suppressed.Further, since the visible light that reaches the deep portion (i.e.,the non-columnar crystalline domain) of the scintillator 500 also isreflected toward the side of the radiation detecting unit 502 by thenon-columnar crystals 500 b, the emitted amount of visible lightincident on the radiation detecting unit 502 (and the detectionefficiency of visible light emitted by the scintillator 500) can beenhanced.

If the thickness of the columnar crystalline domain positioned on theside of the irradiated surface 32 of the scintillator 500 is set at t1,and the thickness of the non-columnar crystalline domain positioned onthe side of the vapor deposition substrate 504 of the scintillator 500is set at t2, then preferably, between t1 and t2, the relationship0.01≦(t2/t1)≦0.25 is satisfied.

In this manner, by satisfying the foregoing relationship between thethickness t1 of the columnar crystalline domain and the thickness t2 ofthe non-columnar crystalline domain, the ratio along the thicknessdirection of the scintillator 500 between a domain (columnar crystallinedomain) of high light emission efficiency for preventing diffusion ofvisible light and a domain (non-columnar crystalline domain) forreflecting visible light lies within a suitable range, whereby the lightemission efficiency of the scintillator 500, the detection efficiency ofvisible light emitted by the scintillator 500, and the resolution of theradiographic image are improved.

If the thickness t2 of the non-columnar crystalline domain is excessive,a domain is increased in which the light emission efficiency is low, andthe sensitivity of the radiation detecting device 22 also is lowered.Therefore, a range in which the quantity t2/t1 is greater than or equalto 0.02 and less than or equal to 0.1 is particularly preferable.

Further, an explanation has been given above concerning a scintillator500 having a structure in which the columnar crystalline domain and thenon-columnar crystalline domain are formed continuously. However, astructure may be provided in which, in place of the aforementionednon-columnar crystalline domain, a light reflective layer is formed fromaluminum (Al) or the like, and only the columnar crystalline domain isformed. Other structures apart therefrom may also be provided.

The radiation detecting unit 502 serves to detect visible light that isradiated out from the light-emitting side (columnar crystals 500 a) ofthe scintillator 500. As viewed from the side in FIG. 18A, an insulatingsubstrate 508, a TFT layer 510, and photoelectric conversion devices 512are stacked in this order with respect to the irradiated surface 32,along the direction in which radiation 16 a through 16 g is irradiated.A planarization layer 514 is formed on the bottom surface of the TFTlayer 510 so as to cover the photoelectric conversion devices 512.

Further, the radiation detecting unit 502 is constituted as a TFT activematrix substrate (hereinafter referred to as a TFT substrate), in whicha plurality of pixels 520, each comprising a photoelectric conversiondevice 512 made from a photodiode (PD) or the like, a storage capacitor516, and a thin film transistor (TFT) 518, are formed in a matrix asviewed in plan on the insulating substrate 508.

Furthermore, the photoelectric conversion device 512 is constituted byarranging a photoelectric conversion film 512 c between a lowerelectrode 512 a on the side of the scintillator 500, and an upperelectrode 512 b on the side of the TFT layer 510.

Still further, the TFT 518 of the TFT layer 510 includes a stackedassembly made up of a gate electrode, a gate insulating film, and anactive layer (channel layer), and a source electrode and a drainelectrode disposed on the active layer are spaced from each other with agap therebetween.

Further, in the radiation detecting unit 502 that makes up the TFTsubstrate, a planarization layer 514 for making the radiation detectingunit 502 planar in shape is formed on a side opposite to the arrivaldirection of the radiation 16 a through 16 g (on the side of thescintillator 500).

In the following descriptions, in the case that the radiation detector300 of the sixth modification is contrasted with the radiation detector170 of the fifth modification, respective constituent elements of theradiation detector 300 correspond respectively with each of theconstituent elements of the radiation detector 170.

First, the insulating substrate 508 corresponds with the substrate 172.However, the insulating substrate 508 is not limited as long as it islight transmissive, and is made of a material that absorbs only a smallamount of radiation 16 a through 16 g.

In the case that a glass substrate is used as the insulating substrate508, the thickness of the radiation detecting unit 502 (TFT substrate)overall is on the order of, for example, 0.7 mm. However, according tothe sixth modification, considering making the radiation detectingdevice 22 thinner in profile, a thin profile substrate made from a lighttransmissive synthetic resin is used as the insulating substrate 508. Asa result, the thickness of the radiation detecting unit 502 overall canbe made thinner in profile on the order, for example, of 0.1 mm, wherebythe radiation detecting unit 502 can be made to possess flexibility.Further, by making the radiation detection unit 502 flexible, resistanceto shocks of the radiation detecting device 22 is improved, and it ismore difficult for the radiation detecting device 22 to suffer damage ifshocks are applied thereto. Further, plastic resins, aramid,bionanofibers and the like tend not to absorb radiation 16 a through 16g, and in the case that the insulating substrate 508 is formed from suchmaterials, since only a small amount of radiation 16 a through 16 g isabsorbed by the insulating substrate 508, even with a structure in whichradiation 16 a through 16 g passes through the insulating substrate 508as a result of being an ISS type of radiation detector, lowering insensitivity with respect to radiation 16 a through 16 g can besuppressed.

With the radiation detecting device 22, it is not essential to utilize asynthetic resin as the insulating substrate 508, and although thethickness of the radiation detecting device 22 will be increased, othermaterials such as a glass substrate or the like may be used as theinsulating substrate 508.

The pixel 520 corresponds to the signal output section 174, and thephotoelectric conversion device 512 corresponds to the sensor 176. Owingthereto, the storage capacitor 516 of the pixel 520 corresponds to thecapacitor 192 of the signal output section 174, and the TFT 518corresponds to the thin film transistor 194. Further, the lowerelectrode 512 a of the photoelectric conversion device 512 correspondsto the upper electrode 182 of the sensor 176, the photoelectricconversion film 512 c corresponds to the photoelectric conversion film186, and the upper electrode 512 b corresponds to the lower electrode184.

Stated otherwise, each of the constituent elements of the ISS typeradiation detector 300 shown in the sixth modification corresponds ingeneral with each of the constituent elements of the PSS type radiationdetector 170 shown in the fifth modification. Accordingly, if thematerials used for the constituent elements of the radiation detector170, which have been described in relation to FIGS. 16 and 17, areapplied as materials for the constituent elements corresponding to theradiation detector 300 of the sixth modification, then the same effectsaccording to each of the materials explained with reference to FIGS. 16and 17 can easily be obtained.

However, different from a PSS type, in an ISS type of radiationdetector, because radiation 16 a through 16 g passes through theradiation detecting unit 502 to arrive at the CsI(Tl) scintillator 500,it is necessary that the radiation detecting unit 502 overall, includingthe insulating substrate 508, the pixels 520 and the photoelectricconversion devices 512, be constituted from materials that absorb only aslight amount of radiation 16 a through 16 g.

Accordingly, in the sixth modification, in the case that thephotoelectric conversion film 512 c is constituted from an organicphotoelectric conversion material, since the photoelectric conversionfilm 512 c absorbs almost no radiation 16 a through 16 g, in an ISS typeof radiation detector in which the radiation detecting unit 502 thereofis arranged so as to permit radiation 16 a through 16 g to passtherethrough, attenuation of radiation 16 a through 16 g that passesthrough the radiation detecting unit 502 can be suppressed, and loweringin sensitivity with respect to the radiation 16 a through 16 g can alsobe suppressed. Accordingly, constituting the photoelectric conversionfilm 512 c from an organic photoelectric conversion material ispreferable, particularly for an ISS type of radiation detector.

[Structures of Second Embodiment]

Next, a radiographic image capturing system 10B according to a secondembodiment, in relation to a radiographic image capturing method, willbe described with reference to FIGS. 19 through 41B.

In the second embodiment, structural elements thereof, which are thesame as those of the first embodiment (see FIGS. 1 through 18B) aredesignated by the same reference numerals, and detailed explanations ofsuch features are omitted. Further, where necessary, in the descriptionof the second embodiment, explanations shall also be made with referenceto FIGS. 1 through 18B.

In outline form, the radiographic image capturing system 10B accordingto the second embodiment differs from the first embodiment in thefollowing points.

More specifically, as shown in FIGS. 19 through 22B, in the secondembodiment, the radiation output device 20 includes three radiationsources 18 a through 18 c (at least two radiation sources). In the casethat a radiographic image is captured with respect to the subject 14, atfirst, a first image capturing process is carried out, in whichradiation (radiation 16 a through 16 c in FIGS. 21A and 22A) is appliedto the subject 14 from at least one of the radiation sources (theradiation sources 18 a through 18 c in FIGS. 21A and 22A) from among theat least two radiation sources. Using the radiation detector 60, bydetecting the radiation that has passed through the subject 14, aradiographic image (first radiographic image) is acquired in the firstimage capturing process. Next, in a case that the dose of radiation bythe first image capturing process shown in the first radiographic imagedoes not reach an optimum dose with respect to the subject 14, radiationdoses are weighted with respect to all of the radiation sources housedin the radiation output device 20 so as to supplement an insufficiencyin the doses of radiation. Thereafter, radiation is applied (secondimage capturing process) with respect to the subject 14 from therespective radiation sources in accordance with the aforementionedweighting, whereby a radiographic image in the second image capturingprocess (second radiographic image) is acquired.

The first embodiment differs from the second embodiment basically asdescribed above. Next, the structure of the second embodiment shall bedescribed in further detail below.

Concerning the second embodiment, FIGS. 21A and 21B show a case in whicha chest region of the subject 14, as a comparatively large region to beimaged, is captured, whereas FIGS. 22A and 22B show a case in which ahand (right hand) region of the subject 14, as a comparatively smallregion to be imaged, is captured.

In the second embodiment, similar to the first embodiment, in the casethat a portable radiation output device 20 is operated inside a hospitalor at a location outside of the hospital, because securing a powersupply may be difficult, preferably, each of the radiation sources 18 athrough 18 c is a battery driven field-emission type radiation source.Accordingly, the respective radiation sources 18 a through 18 c aresmall in size and lightweight, and together therewith, the radiationoutput from the radiation sources 18 a through 18 c has a smallradiation dose. Thus, at the location where image capturing isperformed, the doctor 26 must locate the radiation output device 20 asclosely as possible to the subject 14, such that capturing ofradiographic images is carried out with respect to the subject 14 in astate where the source-to-image distance (SID) is short. As a result,because the radiation 16 a through 16 c emitted from the respectiveradiation sources 18 a through 18 c is applied within a narrowirradiation range, and exposure dose to the subject 14 is small, casesoccur in which radiographic images of an exposure dose suitable fordiagnostic interpretation by the doctor 26 cannot be obtained.

More specifically, in the case that a first image capturing process isperformed with respect to a region to be imaged of the subject 14,because the radiation dose of the radiation 16 a through 16 c withrespect to the region to be imaged is small, if one wishes to obtain aradiographic image of an exposure dose sufficient to enable diagnosticinterpretation of the image, it is necessary to retake the images, i.e.,to perform a second image capturing process. However, if the secondimage capturing process is carried out, in which radiation 16 a through16 c of a large radiation dose is applied to the region to be imaged,then cases could occur in which the cumulative exposure dose of thesecond image capturing process (the first image capturing process andthe second image capturing process) exceeds the exposure dose suitablefor image diagnosis, and the subject 14 is exposed to radiationunnecessarily.

On the other hand, in the case that the subject 14 is irradiated with anoptimum dose (exposure dose) of radiation depending on the region to beimaged of the subject 14 and the thickness of the region to be imaged, aradiographic image can be obtained based on an exposure dose, which issuitable to enable the doctor 26 to diagnostically interpret theresultant radiation image correctly, and together therewith, the subject14 can avoid undue exposure to radiation.

With the second embodiment, at least two radiation sources (threeradiation sources 18 a through 18 c in FIGS. 19 to 23) are disposed inthe radiation output device 20.

Additionally, in the case that a radiographic image is to be captured ofthe subject 14, initially, the first radiographic image capturingprocess is performed, for applying radiation (radiation 16 a through 16c shown in FIGS. 21A and 22A) of a predetermined dose to the subject 14from at least one of the radiation sources (the radiation sources 18 athrough 18 c shown in FIGS. 21A and 22A) among the at least tworadiation sources. At least one source of radiation that has passedthrough the subject 14 is detected by the radiation detector 60, andconverted into a radiographic image (first radiographic image) in thefirst image capturing process. In addition, the region to be imaged ofthe subject 14, which is reflected in the obtained first radiographicimage, is identified.

Next, in the second embodiment, an optimum radiation dose with respectto the identified region to be imaged of the subject 14 (an exposuredose that produces a radiographic image suitable for diagnosticinterpretation by the doctor 26) and a radiation dose with respect tothe region to be imaged of the subject 14 applied during the first imagecapturing process shown in the first radiographic image are compared,and a judgment is made as to whether or not the radiation dose of thefirst image capturing process has reached the optimum radiation dose.

If the radiation dose of the first image capturing process has reachedthe optimum dose, then since the first radiographic image already is aradiographic image suitable for diagnostic interpretation by the doctor26, retaking of the image is unnecessary. On the other hand, if theradiation dose of the first image capturing process has not reached theoptimum dose, then since the first radiographic image is not aradiographic image suitable for diagnostic interpretation by the doctor26, retaking of the image (the second image capturing process) is judgedto be necessary.

Next, in the second embodiment, in the event that the second imagecapturing process is carried out, at first, the difference between theoptimum radiation dose and the radiation dose of the first imagecapturing process is calculated as a dosage insufficiency (insufficiencyin the dose of radiation). Next, based on the dosage insufficiency andthe region to be imaged of the subject 14 identified from the firstradiographic image, weighting is performed with respect to all of theradiation sources housed in the radiation output device 20. Thereafter,in accordance with the aforementioned weighting, application ofradiation (the second image capturing process) is carried out withrespect to the subject 14 from the respective radiation sources, wherebythe radiographic image (second radiographic image) formed by the secondimage capturing process is acquired.

More specifically, with the second image capturing process being appliedwith respect to a comparatively large region (the chest region) as shownin FIG. 21B, it is necessary that radiation 16 a through 16 c be appliedto a comparatively wide area (the entirety of the imaging area 36), suchthat radiation 16 a through 16 c is applied to the entire chest region.Additionally, it is necessary that the cumulative exposure dose withrespect to the subject 14 be the optimum dose (i.e., an exposure doessuitable for diagnostic interpretation by the doctor 26) correspondingto the chest region, the thickness thereof, etc.

Consequently, with the second embodiment, by means of the second imagecapturing process with respect to the comparatively large region to beimaged shown in FIG. 21B, weighting is carried out such that the dosesof the radiation 16 a, 16 c emitted from the radiation sources 18 a, 18c at both ends are maximum (shown by the thick one-dot-dashed line inFIG. 21B), whereas the dose of the radiation 16 b emitted from thecentral radiation source 18 b is smaller, of a degree sufficient tosupplement the maximum dose level (shown by the thin one-dot-dashed linein FIG. 21B). In accordance with such weighting, radiation 16 a through16 c from the respective radiation sources 18 a through 18 c isirradiated simultaneously or sequentially.

On the other hand, with the second image capturing process being appliedwith respect to a comparatively small region (the right hand) as shownin FIG. 22B, since the right hand is positioned in a central portioninside of the imaging area 36, radiation 16 a through 16 c may beapplied reliably only to a comparatively narrow area that includes theaforementioned central portion. In this case also, the cumulativeexposure dose with respect to the subject 14 during the second imagecapturing process must be the optimum dose (i.e., an exposure doessuitable for diagnostic interpretation by the doctor 26) correspondingto the right hand, the thickness thereof, etc.

Consequently, with the second embodiment, by means of the second imagecapturing process with respect to the comparatively small region to beimaged shown in FIG. 22B, weighting is carried out such that the dose ofthe radiation 16 b emitted from the central radiation source 18 b ismaximum (shown by the bold one-dot-dashed line in FIG. 22B), whereas thedoses of the radiation 16 a, 16 c emitted from the radiation sources 18a, 18 c at both ends are smaller, of a degree sufficient to supplementthe maximum dose level (shown by the fine one-dot-dashed line in FIG.22B). In accordance with such weighting, radiation 16 a through 16 cfrom the respective radiation sources 18 a through 18 c is irradiatedsimultaneously or sequentially.

In the case that radiation 16 a through 16 c, the doses of which havebeen weighted in the foregoing manner, is applied to the image capturingregion of the subject 14, radiation 16 a through 16 c that has passedthrough the image capturing region is detected by the radiation detector60 and converted into the second radiographic image.

In the above explanations, the maximum radiation dose is defined as aradiation dose that is comparatively largest in the case that the dosesof radiation 16 a through 16 c are compared, and the small radiationdose is defined as a radiation dose that is comparatively smaller in thecase that the doses of radiation 16 a through 16 c are compared, suchthat none of the dosages is in excess of the optimum radiation dose orthe aforementioned dosage insufficiency. More specifically, according tothe second embodiment, in the second image capturing process of FIGS.21B and 22B, the doses of radiation 16 a through 16 c emitted from therespective radiation sources 18 a through 18 c are weighted, such thatthe cumulative exposure dose, at the time that the subject 14 is exposedto radiation by respectively applying the radiation 16 a through 16 c,becomes the optimum dose.

Also in the second embodiment, as in the first embodiment, as a matterof course, portions of the irradiation ranges of radiation (radiation 16a through 16 c shown in FIGS. 21B and 22B) emitted from adjacentradiation sources overlap mutually with each other, so that radiation isapplied without gaps with respect to the region to be imaged of thesubject 14.

In the second embodiment, in a case where it is difficult for radiation16 a through 16 c to be applied simultaneously, in accordance with theability to supply electric power to the radiation sources 18 a through18 c, or the image capturing conditions (number of images to becaptured) of the subject 14, the radiation sources 18 a through 18 c maysequentially apply radiation 16 a through 16 c respectively, so as toreliably capture a radiographic image of the subject 14. If theradiation sources 18 a through 18 c sequentially apply radiation 16 athrough 16 c respectively, then a central portion of the region to beimaged, which has been positioned, may be irradiated initially, andthereafter, other portions may be irradiated, with the aim of lesseningblurring of the radiographic image, which may be caused by movement ofthe region to be imaged during the image capturing process.Alternatively, the region to be imaged may be irradiated initially withradiation, as indicated by the thick one-dot-dashed lines in FIGS. 21Band 22B, and then be irradiated with radiation, as indicated by the thinone-dot-dashed lines.

Accordingly, with the second embodiment, the simultaneous application ofradiation or the sequential application of radiation may be selecteddepending on the ability to supply electric power with respect to eachof the radiation sources 18 a through 18 c and the image capturingconditions of the subject 14.

Next, concerning internal details of the radiation output device 20, theradiation detecting device 22, and the control device 24 of theradiographic image capturing system 10B, only differences with the firstembodiment will be described in detail below with reference to the blockdiagrams shown in FIGS. 23 and 24.

The radiographic image capturing system 10B according to the secondembodiment differs from the radiographic image capturing system 10A(FIGS. 6 and 7) according to the first embodiment in that the radiationoutput device 20 has three radiation sources 18 a through 18 c and thatthe control processor 124 of the control device 24 has an additionprocessor 148.

In this case, the image capturing condition storage unit 136 storestherein image capturing conditions in the first image capturing process(first image capturing conditions) and image capturing conditions in thesecond image capturing process (second image capturing conditions) forapplying radiation 16 a through 16 c to a region to be imaged. The imagememory 138 stores therein first and second radiographic images, whichhave been transmitted wirelessly from the radiation detecting device 22.

The addition processor 148 carries out addition processing on (digitaldata of) the first radiographic image and (digital data of) the secondradiographic image, data of which are stored in the image memory 138,whereby a radiographic image is generated, which is suitable fordiagnostic interpretation by the doctor 26.

The database 134 stores therein object data representative of aplurality of regions to be imaged as shown in FIG. 25, and tablesconcerning weighting of the doses of radiation 16 a through 16 c asshown in FIGS. 9 and 26. In the second embodiment, three radiationsources 18 a through 18 c are housed in the radiation output device 20,and the grouping procedure as in the first embodiment is not carried outwith respect to the radiation sources 18 a through 18 c. Accordingly,the database 134 does not store therein the table as shown in FIG. 10.

FIG. 25 shows object data representative of radiographic images of aplurality of regions to be imaged. The object data shown in FIG. 10includes object data of a chest, as a relatively large region to beimaged, and object data of right and left hands, as relatively smallregions to be imaged.

So as to correspond to FIG. 9, a table in FIG. 26 shows by way ofexample data representing a chest and a hand, and two and threeradiation sources used to emit radiation. For example, if the number ofradiation sources used is three, then the weighting data “A” correspondsto the radiation source 18 a, the weighting data “B” corresponds to theradiation source 18 b, and the weighting data “C” corresponds to theradiation source 18 c. If the number of radiation sources used isgreater than three, then the number of weighting data in the table shownin FIG. 26 increases depending on the number of radiation sources.

According to the second embodiment, for capturing a radiographic imageof the region to be imaged of the subject 14 (image capturingtechnique), which is represented by the order information, the databaseretriever 150 performs the following processes:

In the case that a first radiographic image is obtained by a first imagecapturing process, the database retriever 150 automatically retrieves,from the database 134, object data that agree with the region to beimaged of the subject 14 reflected in the first radiographic image. Theregion to be imaged, which is represented by the object data that agreewith the region to be imaged, is identified as a region to be imaged ofthe subject 14 during a process of capturing the second radiographicimage. More specifically, the database retriever 150 matches the regionto be imaged reflected in the first radiographic image and therespective object data according to a known pattern matching process,for example, and if a correlation (degree of coincidence) between thetwo images exceeds a predetermined threshold value, identifies a regionto be imaged, which is represented by object data the degree ofcoincidence of which has exceeded the threshold value, as a region to beimaged of the subject 14 in the second radiographic image.

In a case where the database retriever 150 retrieves, from the database134, a plurality of object data, which are highly likely to agree withthe region to be imaged in the first radiograph image (i.e., a pluralityof object data the degree of coincidence of which has exceeded thethreshold value), then the database retriever 150 may display the firstradiographic image and the plural object data on the display unit 126.In this case, the doctor 26 may confirm the content displayed on thedisplay unit 126, and operate the operating unit 128 in order to selectobject data that appear to agree most closely with the region to beimaged in the first radiographic image. The database retriever 150 maythen identify the region to be imaged, which is represented by theselected object data, as a region to be imaged of the subject 14.

The database retriever 150 also identifies the thickness of the regionto be imaged of the subject 14, and an image capturing techniquetherefor. More specifically, if the region to be imaged of the subject14, which is included in the order information stored in the orderinformation storage unit 132, and the identified region to be imaged ofthe subject 14 are in agreement with each other, then the databaseretriever 150 identifies the thickness of the region to be imaged of thesubject 14 and the image capturing technique therefor, which areincluded in the order information, as the thickness of the region to beimaged of the subject 14 and the image capturing technique therefor inthe second image capturing process.

If the identified region to be imaged is not in agreement with theregion to be imaged of the subject 14 that is included in the orderinformation, or if the thickness of the region to be imaged and an imagecapturing technique therefor are desired to be reset, then the databaseretriever 150 may display the identified region to be imaged of thesubject 14 and the order information on the display unit 126. In thiscase, the doctor 26 confirms the displayed content, and operates theoperating unit 128 in order to enter a thickness of the region to beimaged and an image capturing technique therefor. Consequently, thedatabase retriever 150 identifies the entered thickness of the region tobe imaged of the subject 14 and the entered image capturing techniquetherefor, as the thickness of the region to be imaged of the subject 14and the image capturing technique therefor in the second image capturingprocess. The database retriever 150 can also store the entered thicknessof the region to be imaged and the entered image capturing techniquetherefor as part of the order information in the order informationstorage unit 132, thereby editing the order information.

The database retriever 150 also automatically retrieves, from the tableshown in FIG. 9, optimum radiation dose data based on the identifiedregion to be imaged of the subject 14, the thickness thereof, and theimage capturing technique therefor. The database retriever 150 alsoautomatically retrieves optimum weighting data based on the region to beimaged of the subject 14, the image capturing technique therefor, andthe number of radiation sources used in the radiation output device 20.

In addition, the database retriever 150 determines whether or not theexposure dose with respect to the region to be imaged by the first imagecapturing process has reached the optimum radiation dose, by comparingthe optimum radiation dose indicated by the retrieved optimum dose dataand the dose of radiation at the location of the region to be imaged ofthe subject 14 reflected in the first radiographic image. Alternatively,in place of comparing radiation doses per se, the database retriever 150may compare a value (pixel value) of the digital data of theradiographic image corresponding to the optimum radiation dose with avalue (e.g., an average of the pixel value) of the digital data at thelocation of the region to be imaged in the first radiographic image,whereby it can be determined whether or not the exposure dose withrespect to the region to be imaged by the first image capturing processhas reached the optimum radiation dose.

If the exposure dose by the first image capturing process has reachedthe optimum dose, then since the first radiographic image is suitable toenable diagnostic interpretation thereof by the doctor 26, the databaseretriever 150 determines that it is unnecessary to recapture images(i.e., to perform the second image capturing process).

On the other hand, if the exposure dose by the first image capturingprocess has not reached the optimum dose, then since the firstradiographic image is not suitable to enable diagnostic interpretationthereof, the database retriever 150 determines that it is necessary toperform image capturing a second time, and calculates the differencebetween the optimum exposure dose and the exposure dose of the firstimage capturing process as a radiation dosage insufficiency.

Then, the database retriever 150 outputs to the image capturingcondition setting unit 152 the radiation dosage insufficiency, theretrieved optimum radiation dose data and the retrieved weighting data,together with the order information that was used to retrieve the data,which includes the region to be imaged of the subject 14, the thicknessthereof, and the image capturing technique therefor.

If the database retriever 150 retrieves, from the database 134, aplurality of candidates as optimum radiation dose data and weightingdata, then the database retriever 150 displays a plurality of candidatesand the order information on the display unit 126. The doctor 26 mayconfirm the plural candidates and the order information displayed on thedisplay unit 126, and operate the operating unit 128 in order to selectdata that appears to be optimum for the second exposure process. In thiscase, the database retriever 150 then outputs the optimum radiation dosedata and the weighting data, which the doctor 26 has selected from amongthe plural candidates, and the order information to the image capturingcondition setting unit 152. Together therewith, a difference between theoptimum radiation dose indicated by the selected optimum dose data andthe exposure dose during the first image capturing process iscalculated, and the difference after calculation thereof is output tothe image capturing condition setting unit 152 as a radiation dosageinsufficiency.

In the first image capturing process, the image capturing conditionsetting unit 152 automatically sets image capturing conditions (firstimage capturing conditions) for the region to be imaged of the subject14 during the first image capturing process, based on the orderinformation, and stores the set first image capturing conditions in theimage capturing condition storage unit 136. Further, in the second imagecapturing process, the image capturing condition setting unit 152automatically sets the image capturing conditions (second imagecapturing conditions) with respect to the region to be imaged of thesubject 14 during the second image capturing process, based on optimumradiation dose data and the weighting data retrieved by the databaseretriever 150, the order information, and the radiation dosageinsufficiency, and stores the set second image capturing conditions inthe image capturing condition storage unit 136.

At a time of carrying out the second image capturing process, the imagecapturing condition setting unit 152 may display the order information,the optimum radiation dose data and the weighting data retrieved by thedatabase retriever 150, and the radiation dose insufficiency on thedisplay unit 126. The doctor 26 may then confirm the content displayedon the display unit 126, and operate the operating unit 128 in order tochange details of the weighting data depending on the order information,the state of the subject 14, or the image capturing technique. The imagecapturing condition setting unit 152 may then set the second exposureconditions based on the weighting data that have been changed.

Further, during the first image capturing process, the databaseretriever 150 may output to the image capturing condition setting unit152 the optimum radiation dose data corresponding to the region to beimaged of the subject 14, the thickness thereof and the image capturingtechnique, and the image capturing condition setting unit 152 may setthe first image capturing conditions based on the order information andthe optimum radiation dose data.

In the foregoing description, a case has been explained in which thedatabase retriever 150 retrieves optimum radiation dose data from thedatabase 134, and the image capturing condition setting unit 152 setsthe second image capturing conditions based on the retrieved optimumradiation dose data and the like. However, in place of this explanation,after the region to be imaged of the subject 14, which is reflected inthe first radiographic image, has been identified, the databaseretriever 150 can calculate the optimum radiation dose corresponding tothe region to be imaged, based on the image, which shows therein theidentified region to be imaged. In this case, the database retriever 150outputs to the image capturing condition setting unit 152 optimumradiation dose data indicated by the calculated optimum radiation dose,the weighting data retrieved from the database 134, the orderinformation including the region to be imaged of the subject 14, and theradiation dosage insufficiency, whereupon the image capturing conditionsetting unit 152 sets the second image capturing conditions based onsuch information.

[Operations of Second Embodiment]

The radiographic image capturing system 10B according to the secondembodiment is basically constructed as described above. Next, operations(a radiographic image capturing method) of the radiographic imagecapturing system 10B shall be described below with reference to theflowcharts shown in FIGS. 27 and 28.

Herein, an explanation shall be made of a case in which first imagecapturing conditions are set based solely on the order information, andthereafter, the first image capturing process is carried out accordingto the first image capturing conditions, and next, because the exposuredose indicated by the region to be imaged in the first radiographicimage has not reached the optimum radiation dose, a second imagecapturing process is carried out.

First, in step S21 shown in FIG. 27, as in step S1 shown in FIG. 11, thecontrol processor 124 (see FIG. 24) of the control device 24 acquiresorder information from an external source, and stores the acquired orderinformation in the order information storage unit 132.

In step S22, based on the order information, the image capturingcondition setting unit 152 sets the first image capturing conditions,and stores the set first image capturing conditions in the imagecapturing condition storage unit 136.

If the order information does not include the thickness of the region tobe imaged and the image capturing technique therefor in step S22, thenthe doctor 26 (see FIGS. 19 and 20B through 22B) operates the operatingunit 128 in order to enter the thickness of the region to be imaged andthe image capturing technique therefor. The order information storageunit 132 stores the entered thickness of the region to be imaged and theentered image capturing technique therefor as part of the orderinformation, thereby editing the order information in the orderinformation storage unit 132.

Next, in step S23, if the doctor 26 turns on the switch 38 of theradiation detecting device 22 (see FIGS. 21A through 23), then, as instep S6, the battery 76 supplies electric power to various componentsinside the radiation detecting device 22, thereby activating theradiation detecting device 22 in its entirety. As a result, the cassettecontroller 74 sends an activation signal via a wireless link to thecontrol device 24. The battery 76 also applies a bias voltage Vb to therespective pixels 90 of the radiation detector 60.

Based on receipt of the activation signal via the antenna 120 and thecommunication unit 122, the control processor 124 of the control device24 sends the first image capturing conditions, which are stored in theimage capturing condition storage unit 136, to the radiation detectingdevice 22 by way of wireless communications. The cassette controller 74records therein the first image capturing conditions, which are receivedvia the antenna 70 and the communication unit 72.

As in step S6, for positioning the region to be imaged of the subject14, the doctor 26 releases the connection terminals 39, 43 frominterfitting engagement with each other, and also releases theconnection terminals 41, 45 from interfitting engagement with eachother, whereby the radiation output device 20 and the radiationdetecting device 22 become disconnected from each other (see FIG. 2B).At this time, the battery 76 stops charging the battery 68.

Then, the doctor 26 positions the region to be imaged of the subject 14,such that the central position of the region to be imaged of the subject14 and the central position of the imaging area 36 become aligned witheach other, and the region to be imaged of the subject 14 is includedwithin the imaging area 36 (see FIGS. 3A and 3B). Thereafter, the doctor26 grips the grip 28 and orients the radiation output device 20 towardthe region to be imaged of the subject 14, whereby the doctor 26 adjuststhe distance between the radiation output device 20 and the radiationdetecting device 22 to a distance depending on the SID.

As a result, based on a detection signal from the touch sensor 52, theradiation source controller 66 controls the battery 68 in order tosupply electric power to various components of the radiation outputdevice 20, thereby activating the radiation output device 20 in itsentirety. Further, the radiation source controller 66 sends anactivation signal via a wireless link to the control device 24. Based onreceipt of the activation signal via the antenna 120 and thecommunication unit 122, the control processor 124 of the control device24 sends the first image capturing conditions stored in the imagecapturing condition storage unit 136 to the radiation output device 20by way of wireless communications. The radiation source controller 66records the first image capturing conditions, which are received via theantenna 62 and the communication unit 64.

In step S24 after the above preparatory actions have been completed, thedoctor 26 grips the grip 28 with one hand and turns on the exposureswitch 130 with the other hand. The control signal generator 154generates an exposure control signal for starting emission of radiation16 a through 16 c from the radiation sources 18 a through 18 c, andsends the exposure control signal via a wireless link to the radiationoutput device 20 and the radiation detecting device 22. The exposurecontrol signal at the first image capturing process is a synchronizationcontrol signal for capturing the first radiographic image of the regionto be imaged of the subject 14, as a result of synchronizing start ofemission of radiation 16 a through 16 c from the radiation sources 18 athrough 18 c and the detection and conversion of such radiation 16 athrough 16 c into a radiographic image by the radiation detector 60.

Upon receipt of the exposure control signal by the radiation sourcecontroller 66, the radiation source controller 66 controls the radiationsources 18 a through 18 c in order to apply prescribed doses ofradiation 16 a through 16 c to the subject 14 according to the firstimage capturing conditions. The radiation sources 18 a through 18 c emitradiation 16 a through 16 c, which is output from the radiation outputdevice 20 and applied to the region to be imaged of the subject 14, fora given exposure time (irradiation time) based on the first imagecapturing conditions (step S25).

In step S26, radiation 16 a through 16 c passes through the subject 14and reaches the radiation detector 60 in the radiation detecting device22. If the radiation detector 60 is of an indirect conversion type,then, as in step S9, the scintillator of the radiation detector 60 emitsvisible light having an intensity depending on the intensity of theradiation 16 a through 16 c. The pixels 90 of the photoelectricconversion layer 96 convert the visible light into electric signals andstore the electric signals as electric charges therein. The electriccharges (electric charge information), which are stored in the pixels asrepresenting a radiographic image (first radiographic image) of thesubject 14, are read in according with address signals, which aresupplied from the address signal generator 78 of the cassette controller74 to the line scanning driver 100 and the multiplexer 102. The readelectric charge information is amplified respectively by the amplifiers106, sampled by the sample and hold circuits 108, supplied to the A/Dconverter 112 via the multiplexer 102, and converted into digitalsignals. The digital signals, which represent the first radiographicimage, are stored in the image memory 80 (step S27).

Reading operations of the electric charge information from the pixels 90in step S26, and storage of the radiographic image into the image memory80 in step S27 are substantially the same as those in steps S9 and S10,and thus detailed explanation thereof is omitted.

In step S28, as in step S11, the first radiographic image, which isstored in the image memory 80, and the cassette ID information, which isstored in the cassette ID memory 82, are sent to the control device 24wirelessly via the communication unit 72 and the antenna 70. The controlprocessor 124 of the control device 24 stores the first radiographicimage and the cassette ID information, which are received via theantenna 120 and the communication unit 122, in the image memory 138, anddisplays the first radiographic image on the display unit 126.Consequently, the doctor 26, by observing the displayed content on thedisplay unit 126, can confirm that the first radiographic image has beenobtained.

Next, in step S29, the database retriever 150 retrieves automaticallyfrom the database 134 object data that matches with the region to beimaged, which is reflected in the first radiographic image. The regionto be imaged, which is indicated by the object data that agree with theaforementioned region to be imaged, is identified as a region to beimaged of the subject 14 in the second image capturing process.

Next, the database retriever 150 identifies the thickness and the imagecapturing technique in relation to the identified region to be imaged ofthe subject 14. In this case, if the region to be imaged of the subject14 that is included in the order information stored in the orderinformation storage unit 132 and the region to be imaged of the subject14 identified by the database retriever 150 agree with one another, thenthe database retriever 150 identifies, as is, the thickness and theimage capturing technique within the order information as the thicknessand image capturing technique for the region to be imaged of the subject14 in the second image capturing process.

In step S29, if a plurality of object data are retrieved, having adegree of coincidence with the region to be imaged reflected in thefirst radiographic image that has exceeded a predetermined thresholdvalue, then the database retriever 150 may display the firstradiographic image and the plural object data on the display unit 126.The doctor 26 may confirm the content displayed on the display unit 126,and can operate the operating unit 128 in order to select object data,which appear to be in agreement most closely with the region to beimaged in the first radiographic image. The database retriever 150 thenidentifies the region to be imaged, which is represented by the objectdata selected by the doctor 26, as the region to be imaged of thesubject 14.

Further, in step S29, if the region to be imaged of the subject 14,which is reflected in the first radiographic image, is not in agreementwith the region to be imaged of the subject 14, which is included in theorder information, or if the thickness of the region to be imaged of thesubject 14 and the image capturing technique therefor are to be reset,then the database retriever 150 may display on the display unit 126 theidentified region to be imaged of the subject 14 and the orderinformation. The doctor 26 can then confirm the content displayed on thedisplay unit 126, and operate the operating unit 128 in order to enter athickness of the region to be imaged of the subject 14, and an imagecapturing technique therefor. As a consequence, the database retriever150 can identify the entered thickness of the region to be imaged of thesubject 14 and the entered image capturing technique therefor, as thethickness of the region to be imaged of the subject 14 and the imagecapturing technique therefor in the second image capturing process.Further, the database retriever 150 can store the entered thickness ofthe region to be imaged of the subject 14 along with the entered imagecapturing technique therefor, as part of the order information in theorder information storage unit 132, thereby editing the orderinformation store in the order information storage unit 132.

In step S30, as shown in FIG. 28, the database retriever 150 (see FIG.24) automatically retrieves, from the database 134, a region to beimaged of the subject 14, a thickness thereof and image capturingtechnique therefor, which correspond to the region to be imaged of thesubject 14 (see FIGS. 19, and 21A through 23), the thickness thereof,and the image capturing technique therefor that have been identified instep S29 of FIG. 27, along with optimum radiation dose datacorresponding to such items of information. Further, the databaseretriever 150 also automatically retrieves from the database 134weighting data corresponding to the region to be imaged of the subject14 that has been identified in step S29, and the image capturingtechnique therefor.

Next, in step S31, the database retriever 150 compares the optimumradiation dose indicated by the retrieved optimum radiation dose datawith the radiation dose at the location of the region to be imaged ofthe subject 14 in the first radiographic image, and determines whetheror not the exposure dose of the region to be imaged in the first imagecapturing process has reached the optimum radiation dose. In this case,if the exposure dose during the first image capturing process has notreached the optimum radiation dose (step S31: NO), then since a firstradiographic image has not been produced which is suitable fordiagnostic interpretation by the doctor 26, the database retriever 150judges that it is necessary to carry out the second image capturingprocess, and calculates the difference between the optimum exposure doseand the exposure dose during the first image capturing process as aradiation dosage insufficiency (step S32).

Additionally, the database retriever 150 outputs to the image capturingcondition setting unit 152, as various data necessary for the secondimage capturing process, the dosage insufficiency, the retrieved optimumradiation dose data and weighting data, the region to be imaged of thesubject 14 used for retrieval, and the order information including thethickness of the region to be imaged and the image capturing techniquetherefor (step S33).

In step S30, if the database retriever 150 retrieves a plurality ofcandidates for the optimum radiation dose data and the weighting data,then the database retriever 150 may display the plural candidates andthe order information on the display unit 126. In this case, the doctor26 can confirm the content displayed on the display unit 126, and canoperate the operating unit 128 in order to select a candidate (data)that appears to be most optimum for the second image capturing process.The database retriever 150 then regards the optimum radiation dose dataand the weighting data, which the doctor 26 has selected from among theplural candidates, as data necessary for the second image capturingprocess. Together therewith, the database retriever 150 can calculatethe difference between the optimum radiation dose indicated by theselected optimum radiation dose data and the exposure dose of the firstimage capturing process as the radiation dosage insufficiency (stepS32).

In step S34, the image capturing condition setting unit 152 sets thesecond image capturing conditions under which the region to be imaged ofthe subject 14 is to be irradiated with radiation 16 a through 16 cemitted from the radiation sources 18 a through 18 c, based on theentered optimum radiation dose data, the entered weighting data, theorder information, and the dosage insufficiency.

If the region to be imaged of the subject 14 is a chest, as shown inFIG. 21B, then the image capturing condition setting unit 152 (see FIG.24) sets the second image capturing conditions (tube voltages, tubecurrents, and irradiation times) according to the contents of the abovedata, such that the doses of radiation 16 a, 16 c emitted from theradiation sources 18 a, 18 c at the ends are of a maximum dose level,and the dose of radiation 16 b emitted from the radiation source 18 b atthe center is of a lower dose level, sufficient to supplement themaximum dose level, and stores the set second image capturing conditionsin the image capturing condition storage unit 136.

Further, if the region to be imaged of the subject 14 is a hand (righthand), as shown in FIG. 22B, then the image capturing condition settingunit 152 (see FIG. 24) sets the second image capturing conditions (tubevoltages, tube currents, and irradiation times) according to the abovedata, such that the dose of radiation 16 b emitted from the radiationsource 18 b at the center is of a maximum dose level, and the doses ofradiation 16 a, 16 c emitted from the radiation sources 18 a, 18 c atthe ends are of a lower dose level, sufficient to supplement the maximumdose level, and stores the set second image capturing conditions in theimage capturing condition storage unit 136.

In addition, the control processor 124 sends the set second imagecapturing conditions to the radiation output device 20 and the radiationdetecting device 22 (see FIG. 23) wirelessly via the communication unit122 and the antenna 120. The radiation source controller 66 of theradiation output device 20 registers the second image capturingconditions received via the antenna 62 and the communication unit 64,whereas the cassette controller 74 of the radiation detecting device 22registers the second image capturing conditions received via the antenna70 and the communication unit 72.

In step S34, the image capturing condition setting unit 152 may displaythe entered optimum radiation dose data, the entered weighting data, theorder information, and the dosage insufficiency on the display unit 126.The doctor 26 may then confirm the content displayed on the display unit126, and by operating the operating unit 128, can change details of theweighting data depending on the order information, the state of thesubject 14, or the image capturing technique for the subject 14, as wellas setting desired second image capturing conditions in accordance withthe contents of such data, which have been changed. In this case, theimage capturing condition setting unit 152 stores the set second imagecapturing conditions in the image capturing condition storage unit 136.

Further, in the case that, in step S29 of FIG. 27, the databaseretriever 150, after having identified the region to be imaged of thesubject 14 reflected in the first radiographic image, calculates anoptimum radiation dose corresponding to the region to be imaged based onthe image in which the region to be imaged is displayed, and retrievesweighting data from the database 134, then in step S34 of FIG. 28, theimage capturing condition setting unit 152 (see FIG. 24) sets the secondimage capturing conditions based on the order information including theregion to be imaged of the subject 14, the optimum radiation dose dataindicated by the calculated optimum radiation dose, the dosageinsufficiency, and the retrieved weighting data.

Provided that the above preparatory actions have been completed, thedoctor 26 grips the grip 28 with one hand and turns on the exposureswitch 130 with the other hand (step S35). The control signal generator154 generates an exposure control signal for starting emission ofradiation 16 a through 16 c from the radiation sources 18 a through 18c, and sends the exposure control signal via a wireless link to theradiation output device 20 and the radiation detecting device 22 (seeFIG. 23). The exposure control signal of the second image capturingprocess is a synchronization control signal for capturing a secondradiographic image of the region to be imaged of the subject 14, as aresult of synchronizing start of emission of radiation 16 a through 16 cfrom the radiation sources 18 a through 18 c and the detection andconversion of such radiation 16 a through 16 c into a radiographic imageby the radiation detector 60.

Upon receipt of the exposure control signal by the radiation sourcecontroller 66, the radiation source controller 66 controls the radiationsources 18 a through 18 c in order to apply prescribed doses ofradiation 16 a through 16 c to the subject 14 according to the secondimage capturing conditions. The radiation sources 18 a through 18 crespectively emit radiation 16 a through 16 c, which is outputexternally from the radiation output device 20 and applied to the regionto be imaged of the subject 14, for a given exposure time (irradiationtime) based on the second image capturing conditions (step S36).

In this case, if the region to be imaged of the subject 14 is a chest,as shown in FIG. 21B, then the chest is irradiated with large doses ofradiation 16 a, 16 c from the radiation sources 18 a, 18 c at both ends,whereas the region to be imaged is irradiated with a lower dose ofradiation 16 b from the central radiation source 18 b, sufficient tosupplement the large dose level.

Further, if the region to be imaged of the subject 14 is a right hand,as shown in FIG. 22B, then the region to be imaged of the subject 14 isirradiated with a large dose of radiation 16 b from the centralradiation source 18 b, whereas the right hand of the subject 14 isirradiated with lower doses of radiation 16 a, 16 c from the radiationsources 18 a, 18 c at both ends, sufficient to supplement the large doselevel.

Additionally, in step S37, after the radiation 16 a through 16 c haspassed through the subject 14 and reached the radiation detector 60 ofthe radiation detecting device 22, in the case that the radiationdetector 60 is a detector of an indirect conversion type, thescintillator constituting the radiation detector 60 emits visible lightof an intensity corresponding to the intensity of the radiation 16 athrough 16 c, whereupon the respective pixels 90 of the photoelectricconversion layer 96 convert the visible light into electric signals,which are stored as charges. Then, the electric charge information,which is stored in each of the pixels 90 as representing a radiographicimage (second radiographic image) of the subject 14, are read as addresssignals, which are supplied from the address signal generator 78 of thecassette controller 74 to the line scanning driver 100 and themultiplexer 102.

In addition, the second radiographic image made up of the read electriccharge information is stored in the image memory 80 of the cassettecontroller 74 (step S38), and the second radiographic image, which isstored in the image memory 80, and the cassette ID information, which isstored in the cassette ID memory 82, are sent to the control device 24wirelessly via the communication unit 72 and the antenna 70. The controlprocessor 124 of the control device 24 stores the second radiographicimage and the cassette ID information, which are received via theantenna 120 and the communication unit 122, in the image memory 138, anddisplays the second radiographic image on the display unit 126 (stepS39).

Processing of steps S37 through S39 concerning the second radiographicimage are basically the same as steps S26 through S28 concerning thefirst radiographic image. More specifically, since steps S37 through S39can be reproduced simply by replacing terms relating to image capturingof the first radiographic image in the explanations of steps S26 throughS28 with terms relating to image capturing of the second radiographicimage, detailed explanations of steps S37 through S39 have been omitted.

Next, the addition processor 148 carries out a predetermined additionprocess to add the digital data of the first radiographic image and thedigital data of the second radiographic image stored in the image memory138, whereby a radiographic image is generated, which is suitable fordiagnostic interpretation thereof by the doctor 26 (step S40). Thegenerated radiographic image is displayed on the display unit 126,together with being stored in the image memory 138 (step S41). In stepS41, if desired, in addition to the aforementioned radiographic image,the first radiographic image and the second radiographic image, whichwere the subjects of the addition processing, may be displayed togethertherewith.

After having confirmed that a radiographic image suitable for enablingdiagnostic interpretation has been obtained by visually checking thecontent displayed on the display unit 126, the doctor 26 releases thesubject 14 from the positioned condition, and removes the hand from thegrip 28. Owing thereto, the touch sensor 52 stops outputting thedetection signal, and the radiation source controller 66 stops supplyingelectric power from the battery 68 to the various components of theradiation output device 20. As a result, the radiation output device 20is brought into a sleep mode or is shut down. Further, if the doctor 26presses (turns off) the switch 38, then the battery 76 stops supplyingelectric power to the various components of the radiation detectingdevice 22, and the radiation detection device 22 is brought into a sleepmode or is shut down.

Then, the doctor 26 brings the connection terminals 39, 43 intointerfitting engagement with each other, and also brings the connectionterminals 41, 45 into interfitting engagement with each other, therebyholding the radiation output device 20 between the holders 35, 37, so asto integrally combine the radiation output device 20 and the radiationdetecting device 22 with each other (see FIG. 2A).

Moreover, in step S31, if the dose of radiation at the location of theregion to be imaged in the first radiographic image has reached theoptimum radiation dose indicated by the optimum radiation dose dataretrieved by the database retriever 150, in this case, the databaseretriever 150 judges that a radiographic image has been obtained, onlyby carrying out the first image capturing process, which is suitable fordiagnostic interpretation by the doctor 26 (step S31: YES), andthereafter, the first radiographic image is displayed again on thedisplay unit 126 as the radiographic image suitable for enabling imagediagnosis, together with being stored in the image memory 138 (stepS41).

Further, in the case that the size of the dosage insufficiency is solarge as to come near to the optimum dose, as a result of the doseindicated by the first radiographic image being excessively small, thenthe control processor 124, as shown by the broken line in FIG. 28, doesnot implement the addition process (step S40) by the addition processor148, and the process of step S41 is carried out, such that the secondradiographic image, in its present state, is regarded as being aradiographic image suitable to enable diagnostic interpretation thereofby the doctor 26.

[Advantages of Second Embodiment]

As described above, with the radiographic image capturing system 10B andthe radiographic image capturing method according to the secondembodiment, among the at least two radiation sources (i.e., the threeradiation sources 18 a through 18 c, as shown in FIGS. 19 through 23)housed in the radiation output device 20, the first image capturingprocess is carried out with respect to the subject 14 by at least one ofthe radiation sources (i.e., the radiation source 18 a through 18 cshown in FIGS. 21A through 22A). If the radiation dose with respect tothe region to be imaged of the subject 14 indicated in the firstradiographic image obtained from the first image capturing process doesnot reach the optimum dose (i.e., an exposure dose that produces aradiographic image suitable for diagnostic interpretation by the doctor26), then the doses of radiation (radiation 16 a through 16 c) emittedfrom the at least two radiation sources in the second image capturingprocess are weighted, so as to supplement the difference (dosageinsufficiency) between the optimum dose and the dose of the first imagecapturing process.

Accordingly, even though image capturing is carried out a second timewith respect to the region to be imaged of the subject 14, thecumulative exposure dose applied to the region to be imaged of thesubject 14 by the initial image capturing process and the repeated imagecapturing process (the first image capturing process and the secondimage capturing process) becomes equivalent to the optimum dose.

In other words, with the second embodiment, even in the case that imagecapturing is performed again (second image capturing process) withrespect to the subject 14 due to the fact that a desired radiographicimage could not be obtained by the first image capturing process, thesubject 14 is not exposed to radiation unnecessarily.

Further, assuming that the addition processor 148 performs additionprocessing to add the digital data of the first radiographic image andthe digital data of the second radiographic image, a radiographic imagecan easily be obtained of an exposure dosage sufficient to enablediagnostic interpretation of the obtained radiographic image by thedoctor 26.

In this manner, according to the second embodiment, an irradiation rangeof the radiation 16 a through 16 c is not established simply by enablinga region to be imaged of the subject 14 to be covered, but rather, basedon the first radiographic image, radiation doses of radiation 16 athrough 16 c emitted from the respective radiation sources 18 a through18 c are weighted during the second image capturing process.Additionally, because the region to be imaged of the subject 14 isreflected in the first radiographic image, the doses of radiation 16 athrough 16 c are weighted according to the region to be imaged of thesubject 14.

Also, according to the second embodiment, therefore, even if aradiographic image of the subject 14 is captured (by the first andsecond image capturing processes) at a short SID using field-emissionradiation sources, the irradiation range of radiation 16 a through 16 ccan easily be enlarged, and the subject 14 can be irradiated with anoptimum dose (exposure dose) of radiation 16 a through 16 c.

Further, in the second embodiment, if the dose of radiation 16 a through16 c indicated in the first radiographic image has reached the optimumradiation dose, since the first radiographic image already is aradiographic image of an exposure dose sufficient for diagnosticinterpretation by the doctor 26, then naturally, carrying out of thesecond image capturing process (recapturing) becomes unnecessary.

Further, the database retriever 150 identifies the region to be imagedof the subject 14, which is represented by the object data that agreewith the region to be imaged of the subject 14 and which is reflected inthe first radiographic image, as a region to be imaged of the subject 14for the second image capturing process. The database retriever 150 thenretrieves optimum radiation dose data depending on the identified regionto be imaged of the subject 14, the thickness thereof, and the imagecapturing technique therefor, and together therewith, retrievesweighting data depending on the region to be imaged of the subject 14and the image capturing technique therefor. If the radiation dose of theregion to be imaged indicated in the first radiographic image does notreach the optimum radiation dose of the optimum radiation dose data, thedatabase retriever 150 judges that the second image capturing process isneeded and calculates the dosage insufficiency, and thereafter, outputsthe retrieved optimum radiation dose data, the retrieved weighting data,the order information, and the dosage insufficiency to the imagecapturing condition setting unit 152. The image capturing conditionsetting unit 152 is thus capable of setting the second image capturingconditions accurately and efficiently. As a result, as long as theradiation output device 20 applies radiation 16 a through 16 c from therespective radiation sources 18 a through 18 c to the region to beimaged of the subject 14 according to the second image capturingconditions, a second radiographic image, which is sufficient to enablediagnostic interpretation thereof by the doctor 26, can be acquiredreliably.

Further, after the database retriever 150 has identified the region tobe imaged of the subject 14 reflected in the first radiographic image,because it is possible to calculate an optimum radiation dosecorresponding to the region to be imaged based on the image in which theidentified region to be imaged is shown, in the case that the optimumradiation dose data is not stored in the database 134, or even ifdesired optimum radiation dose data cannot be retrieved from thedatabase 134, the optimum radiation dose for the second image capturingprocess can be identified, and based on the identified optimum radiationdose, the second image capturing conditions can be set in the imagecapturing condition setting unit 152.

Further, in the first image capturing and second image capturingprocesses, because the region to be imaged of the subject 14 ispositioned in a central portion of the imaging area 36 (see FIGS. 3A and3B), and is irradiated with radiation 16 a through 16 c, which isdirected toward the region to the imaged of the subject 14 from therespective radiation sources 18 a through 18 c of the radiation outputdevice 20, which confront the central portion, a radiographic image thatcontains the region to be imaged therein can be acquired reliably.

The image capturing condition setting unit 152 may change details of theweighting data retrieved by the database retriever 150, depending on theorder information, the state of the subject 14, or the image capturingtechnique for the subject 14. Thus, more accurate second radiationcapturing conditions can be set depending on the actual image capturingtechnique for the subject 14.

Furthermore, with the second embodiment, if three radiation sources 18 athrough 18 c are housed in the radiation output device 20, during thesecond image capturing process, concerning the radiation 16 a through 16c emitted from the respective radiation sources 18 a through 18 c,weighting of the radiation doses thereof can be performed depending onthe region to be imaged of the subject 14 in the following manner.

As shown in FIG. 21B, if the second image capturing process is performedon a relatively large region to be imaged of the subject 14 (e.g., thechest of the subject 14), then the doses of radiation 16 a through 16 cemitted from the radiation sources 18 a through 18 c are weighted suchthat the doses of radiation 16 a, 16 c emitted from the radiationsources 18 a, 18 c at the ends are of a maximum dose level, whereas thedose of radiation 16 b emitted from the radiation source 18 b at thecenter is of a lower dose level.

As shown in FIG. 22B, if the second image capturing process is performedon a relatively small region to be imaged of the subject 14 (e.g., ahand of the subject 14), then the dose of radiation 16 b emitted fromthe radiation source 18 b at the center is of a maximum dose level,whereas the doses of radiation 16 a, 16 c emitted from the radiationsources 18 a, 18 c at the ends are of a lower dose level.

With the doses of radiation 16 a through 16 c weighted in the foregoingmanner, even if a radiographic image of the subject 14 is captured at ashort SID using field-emission radiation sources 18 a through 18 c, theirradiation range of the radiation 16 a through 16 c can easily beenlarged, and the subject 14 can be irradiated with an optimum dose(exposure dose) of radiation 16 a through 16 c. Since the subject 14 isirradiated with an optimum dose of radiation depending on the subject14, by the addition processor 148 carrying out addition processing onthe first radiographic image and the second radiographic image, it ispossible to acquire a radiographic image suitable for diagnosticinterpretation by the doctor 26, while also preventing the subject frombeing exposed to radiation unnecessarily.

In the example shown in FIG. 21B, image capturing of the secondradiographic image with respect to a relatively large region to beimaged can be carried out efficiently. In the example shown in FIG. 22B,image capturing of the second radiographic image with respect to arelatively small region to be imaged can be carried out efficiently.

The radiographic image capturing system 10B according to the secondembodiment is constituted by the same structural elements as theradiographic image capturing system 10A according to the firstembodiment, and therefore, by providing such structural elements, it isa matter of course that the same advantages and effects of the firstembodiment can be obtained.

[Modifications of the Second Embodiment]

Modifications (seventh through fifteenth modifications) of the secondembodiment will be described below with reference to FIGS. 29A through41B.

Parts of such modifications, which are identical to those shown in FIGS.19 through 28, are denoted by identical reference characters, and suchfeatures will not be described in detail below.

[Seventh Modification]

According to a seventh modification, as shown in FIGS. 29A and 29B, aradiation output device 20 houses two radiation sources 18 a, 18 btherein.

In this case, the radiation sources 18 a, 18 b apply radiation 16 a, 16b respectively to the subject 14. During the second image capturingprocess, doses of radiation 16 a, 16 b are weighted based on the firstradiographic image.

In this manner, in the case of the seventh modification, in which onlytwo radiation sources 18 a, 18 b are housed in the radiation outputdevice 20, by performing the aforementioned first image capturingprocess to acquire the first radiographic image, the same advantages asthose of the second embodiment can be obtained.

As described above, according to the second embodiment and the seventhmodification thereof, a first radiographic image is acquired, and dosesof radiation emitted from two radiation sources 18 a, 18 b or threeradiation sources 18 a, 18 b, 18 c are weighted. However, the firstradiographic image may be acquired, and doses of radiation emitted fromfour or more radiation sources may be weighted based on the principlesof the second embodiment and the seventh modification thereof, therebyoffering the same advantages as those of the second embodiment and theseventh modification.

For example, the second embodiment and the seventh modification may beapplied to the fourth modification (see FIGS. 15A and 15B). Thereby, inthe fourth modification, the same advantages as those of the secondembodiment and the seventh modification can be obtained easily. Further,the advantages derived from the two-dimensional arrangement of theradiation sources 18 a through 18 i, and the advantages derived from thecasing 46 of the radiation output device 20 having substantially thesame rectangular shape as that of the housing 30 of the radiationdetecting device 22 can be obtained.

[Eighth Modification]

According to an eighth modification, as shown in FIGS. 30A and 30B, acasing 46 of the radiation output device 20 includes a recess 164defined in a side thereof remote from the side at which radiation 16 athrough 16 c is emitted from the radiation sources 18 a through 18 c. Acollapsible grip 166 is pivotally movably disposed for storage in therecess 164. A touch sensor 52 is incorporated in the grip 166.

In the case that the doctor 26 is not carrying the radiation outputdevice 20, the grip 166 is accommodated flatwise in the recess 164, asshown in FIG. 30A. If the doctor 26 turns the grip 166 about the pivotedend, then the grip 166 is raised out from the recess 164, so that thedoctor 26 can grip the grip 166 (see FIG. 30B). The grip 166 and thetouch sensor 52 offer the same advantages as those of the grip 28 andthe touch sensor 52 according to the first embodiment. Further, in acase where the grip 166 is turned about the pivoted end back into therecess 164, the grip 166 is placed flatwise in the recess 164, therebykeeping the electrodes of the touch sensor 52 out of contact with thehand of the doctor 26. Therefore, the radiation output device 20 isprevented from being activated, and hence the radiation sources 18 athrough 18 c are prevented from emitting radiation 16 a through 16 c inerror.

[Ninth Modification]

According to a ninth modification, as shown schematically in FIGS. 31Aand 31B, after the first image capturing process is performed, as shownin FIG. 31A, image signals from a portion of the pixels 90 indicated bythe slanted lines are read out intermittently, to thereby obtain thefirst radiographic image. Next, after the second image capturing processis carried out, as shown in FIG. 31B, image signals from all of thepixels 90 indicated by the slanted lines are read out, to thereby obtainthe second radiographic image. More specifically, concerning reading outof image signals from the pixels 90 for the purpose of acquiring thefirst radiographic image, the ninth modification differs from theexample of FIGS. 1 through 30B, in which the first radiographic image isacquired by reading out image signals from all of the pixels 90.

More specifically, the address signal generator 78 (see FIG. 23) of thecassette controller 74 supplies address signals to the line scanningdriver 100 so that only the TFTs 98 (see FIG. 8) connected to the pixels90 indicated by the slanted lines are turned on, and together therewith,the address signals are supplied to the multiplexer 102 in order to readout the image signals from the pixels 90 indicated by the slanted lines.Accordingly, in the case of FIG. 31A, the first radiographic image canbe obtained by supplying control signals via the TFTs 98 only to thegate lines 92 connected to the pixels 90 indicated by the slanted lines,and by reading out image signals from all of the signal lines 94. On theother hand, in the case of FIG. 31B, similar to the case of FIG. 8, thesecond radiographic image can be obtained by supplying control signalsto all of the gate lines 92, and by reading out image signals from allof the signal lines 94.

In this manner, according to the ninth modification, because the imagesignals are read out intermittently (i.e., in a thinned-out manner), thenumber of TFTs 98 that are turned on (i.e., subjected to switching) uponacquisition of the first radiographic image is made smaller, andswitching noise of the TFTs 98 superimposed in the first radiographicimage can be decreased. Accordingly, in the addition processor 148, theradiographic image obtained by carrying out addition processing of thefirst radiographic image and the second radiographic image is renderedas a radiographic image in which switching noise is small, and which issuitable for diagnostic interpretation by the doctor 26.

[Tenth Modification]

According to a tenth modification, as shown schematically in FIG. 32,the radiation detector 60 is constructed by arranging in order along thedirection in which radiation 16 a through 16 c is applied, aphotoelectric conversion layer 96 (first photoelectric conversion layer)including pixels 90 as first solid state detecting elements and TFTs 98,the scintillator 168, and a photoelectric conversion layer 177 (secondphotoelectric conversion layer) including pixels 210 as second solidstate detecting elements and TFTs 212. In the tenth modification,similar to the case of FIG. 8, each of the pixels 90, 210 are arrayed ina matrix form.

Among the pixels 90, 210, at least the pixels 90 are formed using anorganic photoelectric conversion material. As noted above, because theorganic photoelectric conversion material does not absorbelectromagnetic waves other than light emitted by the scintillator 168(because it is transmissive to X-rays), the side on which the pixels 90that utilize the organic photoelectric conversion material are disposedcan serve as a side to which radiation 16 a through 16 c is applied.

On the other hand, a non-organic photoelectric conversion material suchas amorphous silicon or the like possesses the characteristic ofabsorbing X-rays and becomes deteriorated upon absorption of X-rays.Therefore, concerning the pixels 210, which are arranged on the backsurface side in relation to the direction in which radiation 16 athrough 16 c is applied, such pixels 210 may be formed form anon-organic photoelectric conversion material. In this manner, byforming the pixels 90 from an organic photoelectric conversion materialand forming the pixels 210 from a non-organic photoelectric conversionmaterial, the usage life of the pixels 210 can be extended.

Further, because the radiation 16 a through 16 c applied to the side ofthe pixels 90 and which passes through the scintillator 168 is absorbedby the pixels 210 made of a non-organic photoelectric conversionmaterial, the amount of radiation 16 a through 16 c that is leaked fromthe back surface side (side of the pixels 210) can be made small.Furthermore, because the pixels 90 formed by an organic photoelectricconversion material are provided on the side (front surface side)irradiated with radiation 16 a through 16 c, attenuation of theradiation 16 a through 16 c by the pixels 90 can be decreased.Accordingly, radiation 16 a through 16 c can be made incident on thescintillator 168 without undue attenuation thereof.

In the tenth modification in which the radiation detector 60 isconstructed in the manner described above, the address signal generator78 (see FIG. 23) of the cassette controller 74 acquires the firstradiographic image by reading out image signals from all of the pixels210 after the first image capturing process, and next acquires thesecond radiographic image by reading out image signals from all of thepixels 90 after the second image capturing process.

More specifically, immediately after the first image capturing process,image signals are not read out from the pixels 90. On the other hand,immediately after the second image capturing process, image signals arenot read out from the pixels 210, and the second radiographic image,which is read out from all of the pixels 90, becomes the radiographicimage suitable for diagnostic interpretation by the doctor 26.Accordingly, with the tenth modification, the addition process of theaddition processor 148 is unnecessary.

Stated otherwise, the first radiographic image read out from the pixels210 becomes a radiographic image used only for the purpose of theradiation dose weighting of the radiation 16 a through 16 c in thesecond image capturing process. Accordingly, the respective pixels 210function as monitor pixels for acquiring the second radiographic image.

In the foregoing manner, according to the tenth modification, becausethe addition process of the addition processor 148 is unneeded,imposition of switching noise, which occurs upon reading out the firstimage signal, on the second radiographic image (the radiographic imagesuitable for diagnostic interpretation by the doctor 26) can be avoided.Owing thereto, switching noise in the radiographic image that is usedfor diagnostic interpretation can be further reduced.

As noted above, because the respective pixels 210 function as monitorpixels, the photoelectric conversion layer 177 including the pixels 210may make use of a photoelectric conversion layer having defective pixelstherein, a photoelectric conversion layer having coarse pixels, or aphotoelectric conversion layer having a diminished photoelectricconversion function.

[Eleventh Modification]

According to an eleventh modification, as shown in FIGS. 33 and 34, theradiation detecting device 22 further includes a body motion detector214, and the radiation output device 20 additionally incorporates anacceleration sensor 217 therein, and the control processor 124 of thecontrol device 24 further includes an exposure permission determiningunit 216.

The body motion detector 214 detects body movements of (the region to beimaged of) the subject 14, who is positioned with respect to the imagingarea 36 (see FIGS. 2A through 3B). The acceleration sensor 217 detectsacceleration of the radiation output device 20. The exposure permissiondetermining unit 216 determines whether emission of radiation 16 athrough 16 c from the radiation sources 18 a through 18 c (applicationof radiation 16 a through 16 c to the region to be imaged) is permittedor interrupted, based on the detection result of the body motiondetector 214 or the detection result of the acceleration sensor 217.

More specifically, the body motion detector 214 may be at least one of(1) a pressure sensor for detecting pressure imposed on the radiationdetecting device 22 from (the region to be imaged of) the subject 14that is positioned, (2) a vibration sensor for detecting vibration ofthe radiation detecting device 22 caused by movement of the region to beimaged of the subject 14, and (3) a contact sensor for detecting contactof the subject 14 with respect to the radiation detecting device 22. Thephysical value detected by the body motion detector 214 is a physicalvalue related to motion of (the region to be imaged of) the subject 14.In addition, the body motion detector 214 sends the detection signalrepresenting the physical value to the control device 24 by way ofwireless communications from the communication unit 72 via the antenna70.

In the case that the doctor 26 retains the radiation output device 20 bygripping the grip 28, the acceleration sensor 217 sequentially detectsthe acceleration of the radiation output device 20, and sends adetection signal representing the detected acceleration to the controldevice 24 via a wireless link via the communication unit 64 and theantenna 62. The acceleration, which is detected by the accelerationsensor 217, is a physical quantity corresponding to wobbling movementsof the radiation output device 20 retained by the doctor 26.

On the other hand, in the case that the exposure permission determiningunit 216 judges that the change of the pressure with time, the size ofthe vibration, the contact area between the subject 14 and the radiationdetecting device 22, or the acceleration of the radiation output device20, which relate to physical quantities indicative of detection signalsreceived respectively via the antenna 120 and the communication unit122, have exceeded predetermined thresholds, image capturing of theradiographic image with respect to the subject 14 is suspended, and thedisplay unit 126 (notification unit) notifies the doctor 26 that imagecapturing has been suspended.

Next, operations of the eleventh embodiment shall be explained withreference to the flowchart of FIG. 35.

During the first image capturing process, the body motion detector 214sequentially detects the physical quantity concerning movement of theregion to be imaged of the subject 14, and detection signals of thedetected physical quantity are sent sequentially via wirelesscommunications to the control device 24. Further, the accelerationsensor 217 sequentially detects the acceleration of the radiation outputdevice 20, and sequentially sends the detection signal indicative of thedetected acceleration (physical quantity) wirelessly to the controldevice 24. The exposure permission determining unit 216 sequentiallyregisters data of each of the physical quantities indicative of thesequentially received detection signals.

In addition, in step S50, after step S28 (see FIG. 27) in which thefirst image capturing process is completed, the exposure permissiondetermining unit 216 determines whether or not data of the physicalquantities exist, which are in excess of predetermined thresholds amongthe registered data of the respective physical quantities. In the casethat data of a physical quantity is discovered, which is in excess of apredetermined threshold (step S50: YES), then the exposure permissiondetermining unit 216 judges that motion of the region to be imaged ofthe subject 14 or wobbling movement of the radiation output device 20has occurred, which could adversely influence the first radiographicimage captured during the first image capturing process.

Motions of the region to be imaged of the subject 14 or wobblingmovements of the radiation output device 20, which may adverselyinfluence the first radiographic image, are defined, for example, asbody motions in which the region to be imaged is wobbled, or as wobblingmovements of the radiation output device 20, to such an extent that theregion to be imaged cannot be identified upon attempting to identify theregion to be imaged of the subject 14 that is reflected in the firstradiographic image, or alternatively, are defined as body motions inwhich the region to be imaged in the radiographic image is wobbled, oras wobbling movements of the radiation output device 20, to such anextent that weighting processing cannot reliably be carried out uponweighting on the doses of radiation 16 a through 16 c.

Next, in step S51, the exposure permission determining unit 216 notifiesthe doctor 26 via the display unit 126 that the second image capturingstep has been suspended. Further, the exposure permission determiningunit 216 indicates (step S52) via the display unit 126 that recapturingof the radiographic image (carrying out of the first image capturingprocess again) should be implemented. By visual confirmation of thecontent displayed on the display unit 126, the doctor 26 can grasp thatthe first image capturing process has failed, and step S22 is returnedto in preparation for recapturing the first radiographic image.

On the other hand, in step S50, if it is judged that data of thephysical quantities do not exist that are in excess of predeterminedthresholds among the data of the physical quantities registered in theexposure permission determining unit 216 (step S50: NO), the exposurepermission determining unit 216 determines that movement of the regionto be imaged or wobbling of the radiation output device 20 has notoccurred during the first image capturing process, which could adverselyinfluence the first radiographic image. As a result, in the controldevice 24, implementation of the process of step S9 is enabled, andpreparations can progress toward the second image capturing process.

In this manner, according to the eleventh modification, body movementsof the region to be imaged of the subject 14 or wobbling of theradiation output device 20 during the first image capturing process aredetected, and if such body movements or wobbling of the radiation outputdevice 20 are of such an extent as to adversely influence theradiographic image, then a notification (indication) is made to suspendthe second image capturing process and to carry out recapturing, i.e.,to perform the first image capturing process again. Therefore, aradiographic image, which is suitable for diagnostic interpretationthereof by the doctor 26, can be acquired reliably.

The eleventh modification is not limited by the foregoing explanations.For example, the exposure permission determining unit 216 may functionas a wobbling movement amount calculator for calculating an amount ofwobbling of the region to be imaged of the subject 14 in the firstradiographic image, such that if the wobbling amount exceeds apredetermined threshold, a notification (indication) may be given tosuspend the second image capturing process and to perform recapturing ofthe first radiographic image. More specifically, in this case, theexposure permission determining unit 216 functions doubly as a bodymotion detector for detecting movements of the region to be imaged ofthe subject 14.

[Twelfth Modification]

According to a twelfth modification, as shown in FIGS. 36 through 37B,image capturing is performed by means of a web camera 48, which isdisposed in the radiation output device 20, in order to capture a regionto be imaged of the subject 14 having been positioned with respect tothe imaging area 36. Based on the camera image of the region to be imagecaptured by the web camera 48, the exposure permission determining unit216 (see FIG. 34) determines whether to allow or prohibit output ofradiation (application of radiation 16 a through 16 c with respect tothe region to be imaged) from the radiation sources 18 a through 18 c.

Features of the web camera 48 shall be described in further detailbelow.

The web camera 48 serves for imaging a predetermined imaging range 84 inorder to acquire a camera image (optical image) thereof. In this case,the radiation output device 20 and the web camera 48 are integrallycombined with each other.

Integral combination of the radiation output device 20 and the webcamera 48 is not limited to an arrangement in which the web camera 48 ishoused in the radiation output device 20, but refers to any arrangementin which the web camera 48 is integrally joined (connected) to theradiation output device 20, at least when the radiographic imagecapturing system 10B is in use. For example, integral combination of theradiation output device 20 and the web camera 48 includes (1) anarrangement in which the web camera 48 and the radiation output device20 are connected to each other by a cable provided by the radiographicimage capturing system 10B, (2) an arrangement in which the web camera48 and the radiation output device 20 are connected to each other by acable provided by a doctor 26, and (3) an arrangement in which theradiation output device 20 and the web camera 48 are joined to eachother when the radiographic image capturing system 10A is in use, andwherein the radiation output device 20 and the web camera 48 can bedisconnected (separated) from each other when the radiographic imagecapturing system 10A is undergoing maintenance or is not in use.

To make the web camera 48 disconnectable from the radiation outputdevice 20 when the radiographic image capturing system 10A is undergoingmaintenance or is not in use, the web camera 48 may be joined to theradiation output device 20 by a joining means such as a clip or thelike. The web camera 48 may be joined to the radiation output device 20by the joining means only when the radiographic image capturing system10A is in use. The joining means may incorporate a ball joint forenabling the orientation of the web camera 48, which is joined to theradiation output device 20, to be freely changed. If the web camera 48is joined to the radiation output device 20 by the joining means, thenit is necessary for the web camera 48 and the radiation output device 20to be electrically connected to each other via a wired link, e.g., a USBcable, or a wireless link.

If the radiation output device 20 and the web camera 48 are connected toeach other by a cable, then since the web camera 48 can independently beplaced in a desired position within a range defined by the length of thecable, the web camera 48 can be positioned with greater freedom than ifthe web camera 48 were housed in the radiation output device 20.

Further, in the radiation output device 20, the web camera 48 ispositioned closely to the radiation source 18 b. Additionally, if adetection signal is output from the touch sensor 52, the radiationoutput device 20 enables a camera image to be captured with respect toan imaging range 84 of the web camera 48. More specifically, theradiation output device 20 includes a camera controller 86, such that ifthe detecting signal is input to the camera controller 86, the cameracontroller 86 controls the web camera 48 to initiate image capturing ofthe imaging range 84, and the camera image taken by the web camera 48 issent to the control device 24 via wireless communications through thecommunication unit 64 and the antenna 62.

Accordingly, if the doctor 26 grips the grip 28 and orients theradiation output device 20 toward the radiation detecting device 22,image capturing of the imaging range 84, which includes therein theimaging area 36, is enabled. If the region to be imaged of the subject14 is positioned with respect to the imaging area 36, because the regionto be image is positioned inside of the imaging range 84, the web camera48 can capture a camera image in which the region to be imaged isreflected.

The web camera 48 is capable of continuously capturing images of theimaging range 84 so as to capture successive camera images (a movingimage), is capable of intermittently capturing images of the imagingrange 84 at predetermined time intervals so as to acquire camera images(still images) which are captured intermittently, or can acquire acamera image (still image) which is captured at a certain time.

FIG. 37A shows the manner in which the web camera 48 captures an imageof the chest of the subject 14, which is a comparatively large region tobe imaged, whereas FIG. 37B shows the manner in which the web camera 48captures a radiographic image of the hand of the subject 14, which is acomparatively small region to be imaged.

The web camera 48 sends the camera image of the region to be imaged ofthe subject 14 wirelessly to the control device 24 via the communicationunit 64 and the antenna 62. In the case it is judged that the movementamount (physical value) of the region to be imaged of the subject 14 inthe camera image, which is received via the antenna 120 and thecommunication unit 122, has exceeded a predetermined threshold, theexposure permission determining unit 216 suspends image capturing of theradiographic image with respect to the subject 14, and notifies thedoctor 26 through the display unit 126 (notification means) that imagecapturing was suspended.

Additionally, in the twelfth modification, as shown in the flowchart ofFIG. 35, during the first image capturing process, the web camera 48captures a camera image of the imaging range 84, and sends the cameraimage to the control device 24 by way of wireless communications. Theexposure permission determining unit 216 records the received data ofthe camera image in the image memory 138.

In step S50 after step S28 (see FIG. 27) in which the first imagecapturing process is completed, the exposure permission determining unit216 determines whether or not data of the movement amount of a region tobe imaged exists, which is in excess of a predetermined threshold amongdata of the recorded camera images. In the case that data of themovement amount is discovered, which is in excess of the predeterminedthreshold (step S50: YES), then the exposure permission determining unit216 judges that body motion of the region to be imaged of the subject 14has occurred, which could adversely influence the first radiographicimage captured in the first image capturing step, and processing fromstep S51 and steps subsequent thereto are implemented. On the otherhand, in step S50, in the case that data of the movement amount is notdiscovered that is in excess of the predetermined threshold among dataof the camera images recorded in the exposure permission determiningunit 216 (step S50: NO), the exposure permission determining unit 216determines that movement of the region to be imaged has not occurredduring the first image capturing process which could adversely influencethe first radiographic image captured in the first image capturing step,whereupon the control device 24 implements the process of step S29.

In this manner, in the twelfth modification as well, because body motionof the region to be imaged of the subject 14 during the first imagecapturing process is detected by using the camera image, the sameeffects as those of the eleventh modification can be achieved. Further,in the twelfth modification, although the descriptions thereof havecentered on operations of the web camera 48, because the accelerationsensor 217 is incorporated in the radiation output device 20, inaddition to the movement amount of the region to be imaged in the cameraimage captured by the web camera 48, using the acceleration of theradiation output device 20 detected by the acceleration sensor 217, theoccurrence of movement of the region to be imaged, as well as theoccurrence of wobbling motions of the radiation output device 20 mayalso be determined in the exposure permission determining unit 216.

[Other Structures of the Eleventh and Twelfth Modifications]

In the foregoing explanations of the eleventh and twelfth modifications,after the first image capturing process, it is determined whether or notmovement of the region to be imaged of the subject 14 during the firstimage capturing process has occurred, and in the case that such movementis determined to have occurred, the second image capturing process issuspended, and recapturing of the first radiographic image isimplemented.

However, the eleventh and twelfth modifications are not limited by theforegoing explanations, and in the case that the region to be imaged ofthe subject 14 is already moving, or if wobbling of the radiation outputdevice already occurs during preparations for the first image capturingprocess (prior to application of radiation 16 a through 16 c), the firstimage capturing process may be delayed or suspended, and thereafter, thefirst image capturing process can be enabled once such body movements orwobbling have settled down.

More specifically, as shown in the flowchart of FIG. 38, theacceleration (physical quantity) of the radiation output device 20 isdetected by the acceleration sensor 217 during preparation for the firstimage capturing process, and a detection signal indicative of thedetected acceleration is sent wirelessly to the control device 24.Together therewith, a physical quantity relating to the body movement ofthe region to be imaged of the subject 14 is detected by the body motiondetector 214, and a detection signal indicative of the physical quantityis sent wirelessly to the control device 24. Alternatively, the webcamera 48 captures an image of the imaging range 84, and the cameracontroller 86 sends the camera image of the imaging range 84 wirelesslyto the control device 24. In the above cases, in step S60 after step S22(see FIG. 27), the exposure permission determining unit 216 determineswhether or not the physical quantity indicated by the received detectionsignal, or the movement amount of the region to be imaged in thereceived camera image is in excess of a predetermined threshold.

In the case that the physical quantity or the movement amount hasexceeded the aforementioned thresholds, the exposure permissiondetermining unit 216 determines that movement of the region to becaptured of the subject 14, or wobbling of the radiation output device20 has occurred, which could adversely influence the first radiographicimage (step S60: YES), and it is determined to delay or suspend thefirst image capturing process.

In the following step S61, the exposure permission determining unit 216notifies the doctor 26 through the display unit 126 that the first imagecapturing process has been delayed or suspended.

After the notification of step S61, the acceleration sensor 217sequentially detects the acceleration of the radiation output device 20,and continuously sends wirelessly to the control device 24 the detectionsignal indicative of such acceleration. Together therewith, the bodymotion detector 214 sequentially detects the physical quantity relatedto movement of the region to be imaged of the subject 14, andcontinuously sends wirelessly to the control device 24 the detectionsignal indicative of the physical quantity. Alternatively, the webcamera 48 captures an image of the imaging range 84, and the cameracontroller 86 continuously sends wirelessly to the control device 24 thecamera image of the imaging range 84.

Accordingly, in step S62, the exposure permission determining unit 216determines whether or not the physical quantity indicated by thereceived detection signal, or the received amount of movement of theregion to be imaged in the camera is less than the predeterminedthreshold, and more specifically, it is determined whether movement ofthe region to be imaged of the subject 14, or wobbling of the radiationoutput device 20 has settled down or not. If the physical quantity orthe movement amount is less than the threshold value, and it is judgedthat the body motion or wobbling has settled down (step S62: YES), thenthe exposure permission determining unit 216 releases the suspension ordelay of the first image capturing process, and displays on the displayunit 126 a notification to the effect that the first image capturingprocess is permitted (step S63). By visually confirming the contentdisplayed on the display unit 126, the doctor 26 grasps that permissionhas been granted for the first image capturing process, and then it ispossible for step S23 to be implemented.

In step S60, in the event that body movement of the region to be imagedof the subject 14, or wobbling of the radiation output device 20 doesnot occur, since body motion or wobbling does not occur that couldadversely influence the first radiographic image, the exposurepermission determining unit 216 judges that there is no problem for thefirst image capturing process to be carried out (step S60: NO), andimplements the process of step S63.

By applying the process steps shown in FIG. 38 to the eleventhmodification and the twelfth modification, because the firstradiographic image can reliably be acquired, in effect, this enablesacquisition of the second radiographic image, and acquisition of aradiographic image suitable for diagnostic interpretation, to reliablybe carried out.

[Thirteenth Modification]

According to a thirteenth modification, as shown in FIG. 39, the webcamera 48 is separate from the radiation output device 20 and theradiation detecting device 22. In this case, the web camera 48 capturesa camera image of the radiation output device 20, the region to beimaged of the subject 14, and the radiation detecting device 22. The webcamera 48 includes a camera controller 86 and a communication unit 88for sending signals to and receiving signals from an external circuitwirelessly. In this case, if the control processor 124 of the controldevice 24 (see FIG. 24) receives an activation signal from the radiationoutput device 20, the control processor 124 sends a control signal tothe communication unit 88 via a wireless link. The camera controller 86controls the web camera 48 in order to start capturing the imaging range84, based on the control signal received via the communication unit 88.In addition, the camera controller 86 sends to the control device 24wirelessly from the communication unit 88 the camera image captured bythe web camera 48. According to the thirteenth modification, inasmuch asthe radiation output device 20, the radiation detecting device 22, thecontrol device 24, and the web camera 48 are connected wirelessly overthe same wireless link, no cables are required in order for such devicesto send and receive signals.

Accordingly, in the thirteenth modification as well, the same effects asthose of the twelfth modification can easily be obtained.

[Fourteenth Modification]

According to a fourteenth modification, as shown in FIG. 40, the webcamera 48 is incorporated in a control device 24 in the form of aportable terminal, so that the web camera 48 and the control device 24are integrally combined with each other.

The portable control device 24 comprises a laptop or notebook type ofpersonal computer (PC) including a main body 114, which incorporates anoperating unit 128 and a communication unit 122, a cover body 118incorporating therein a display unit 126 and the web camera 48, and ahinge 116 interconnecting the main body 114 and the cover body 118.Therefore, the control device 24 and the web camera 48 are integrallycombined with each other.

Integral combination of the control device 24 and the web camera 48,similar to integral combination of the radiation output device 20 andthe web camera 48, is not limited to an arrangement in which the webcamera 48 is housed in the control device 24, but refers to anyarrangement in which the web camera 48 is integrally joined (connected)to the control device 24, at least when the radiographic image capturingsystem 10B is in use. For example, integral combination of the controldevice 24 and the web camera 48 includes (1) an arrangement in which theweb camera 48 and the control device 24 are connected to each other by acable provided by the radiographic image capturing system 10B, (2) anarrangement in which the web camera 48 and the control device 24 areconnected to each other by a cable provided by the doctor 26, and (3) anarrangement in which the control device 24 and the web camera 48 arejoined to each other when the radiographic image capturing system 10B isin use, and wherein the web camera 48 can be disconnected (separated)from the control device 24 when the radiographic image capturing system10B is undergoing maintenance or is not in use.

To make the web camera 48 disconnectable from the control device 24 whenthe radiographic image capturing system 10A is undergoing maintenance oris not in use, the web camera 48 may be joined to the control device 24by a joining means such as a clip or the like. The web camera 48 may bejoined to the control device 24 by such a joining means only when theradiographic image capturing system 10A is in use. The joining means mayincorporate a ball joint for freely changing the orientation of the webcamera 48 that is joined to the control device 24. If the web camera 48is joined to the control device 24 by such a joining means, then it isnecessary for the web camera 48 and the control device 24 to beelectrically connected to each other by a wired link (e.g., a USB cable)or a wireless link.

If the control device 24 and the web camera 48 are connected to eachother by a cable, then since the web camera 48 can independently beplaced at a desired position within a range defined by the length of thecable, the web camera 48 can be positioned with greater freedom than ifthe web camera 48 were housed in the control device 24.

One side of the main body 114 has an input terminal 142 for connectionto an AC adapter, a card slot 144 for receiving a memory card (notshown) therein, and a USB terminal 146 for connection to a USB cable(not shown).

In a state in which the control device 24 is arranged, such that thecover body 118 is turned away from the main body 114 about the hinge 116in order to orient the web camera 48 toward the radiation output device20, the region to be imaged of the subject 14, and the radiationdetecting device 22, in the event that the control processor 124 (seeFIG. 24) receives an activation signal from the radiation output device20, the control processor 124 outputs a control signal to the cameracontroller 86. Based on the control signal, the camera controller 86controls the web camera 48 in order to start capturing a camera image ofthe imaging range 84. The camera controller 86 then outputs the cameraimage captured by the web camera 48 to the control processor 124.

In this case, since the web camera 48 is incorporated in the controldevice 24, the control device 24 can reliably acquire a camera imagecaptured by the web camera 48. If the control processor 124 incorporatestherein the function of the camera controller 86, then the controlprocessor 124 can directly control the web camera 48. According to thefourteenth modification, inasmuch as the radiation output device 20, theradiation detecting device 22, and the control device 24 are connectedwirelessly over the same wireless link, no cables are required for suchdevices to send and receive signals therebetween.

Thus, in the fourteenth modification as well, the various effects andadvantages of the twelfth and thirteenth modifications can easily beobtained.

[Fifteenth Modification]

Incidentally, in the second embodiment, in the case that the SID is setby moving the radiation output device 20 while the grip 28 is beinggripped by the doctor 26, if the radiation output device 20 is made toapproach the subject 14 too closely, then as shown in FIG. 41A, the SID(the distance SID1 shown in FIG. 41A) becomes too short, and cases occurin which image capturing cannot be carried out with respect to thesubject 14 except within a comparatively narrow range. Further, if theSID is too short, then the respective irradiation ranges of theradiation 16 a through 16 c will not be overlapped on the irradiatedsurface 32, resulting in the possibility that image capturing withrespect to the subject 14 will fail.

Consequently, according to the fifteenth modification, the structure ofthe eleventh and twelfth modifications (see FIGS. 33 through 38) isutilized, whereby based on the acceleration of the radiation outputdevice 20 detected by the acceleration sensor 217, an amount of movementof the radiation output device 20 is calculated, and it is judgedwhether or not the SID is set at an appropriate distance based on thecalculated amount of movement. Then, application of radiation 16 athrough 16 c is permitted, or application of radiation 16 a through 16 cis started at a point in time that the SID becomes set at theappropriate distance.

More specifically, in the case that the doctor 26 grips the grip 28 andthereby adjusts the SID, the acceleration sensor 217 detects theacceleration of the radiation output device 20 successively, and thecontrol processor 124 calculates the amount of movement of the radiationoutput device 20 based on the acceleration detected by the accelerationsensor 217. In the exposure permission determining unit 216, in theevent that the amount of movement calculated by the control processor124 reaches a movement amount corresponding to an appropriate SID (e.g.,the source-to-image distance SID2 shown in FIG. 41B) for capturing animage of the subject 14, output of radiation 16 a through 16 c (therecapturing process in the second embodiment) from each of the radiationsources 18 a through 18 c is permitted. Consequently, image capturingover a comparatively wide range can be carried out with respect to thesubject 14, and image capturing failures with respect to the subject 14can be avoided.

According to the fifteenth modification, (1) output of radiation 16 athrough 16 c from the respective radiation sources 18 a through 18 c maybe started by the doctor 26 pressing the exposure switch 130 after therecapturing process has been permitted by the exposure permissiondetermining unit 216, or (2), since the SID2 is set at a point in timewhen the recapturing process is permitted, output of radiation 16 athrough 16 c from the respective radiation sources 18 a through 18 c maybe started automatically once permission has been granted.

Further, until the source-to-image distance (SID) reaches the SID2, thedoctor 26 may be notified and prompted by the display unit 126 or thelike to move the radiation output device 20, and may be notified andprompted to stop movement of the radiation output device 20 at a pointin time that the SID2 is reached. As a result, in accordance with thenotification content to stop movement, at a point in time that thedoctor 26 stops moving the radiation output device 20 (i.e., when theacceleration detected by the acceleration sensor 217 is of a zerolevel), the exposure permission determining unit 216 can grantpermission to initiate the recapturing process, and thus capturing ofimages with respect to the subject 14 can be carried out immediately.

In the foregoing description of the fifteenth modification, a case hasbeen explained in which recapturing of images in the second embodimentis carried out, however, it is a matter of course that the same effectsand advantages can be obtained in a case where the fifteenthmodification is applied to the case of the first image capturing processof the second embodiment.

[Sixteenth Modification]

Incidentally, during image capturing with respect to the subject 14,because the center position of the image capturing region of the subject14 substantially matches the center position of the imaging area 36, andfurther, since the image capturing region is positioned so as to fitwithin the imaging area 36, a large number of cases occur in which theregion of interest (ROI) is positioned at the center of the imaging area36.

Thus, in the first embodiment, cases are frequent in which an imagecapturing process is carried out with respect to the subject 14, suchthat the doses of radiation emitted from the radiation sources that arepositioned near the geometric center position in the radiation outputdevice 20 (the radiation sources included in the group 56 or in thegroups 158, 160) are set at a large dose level, whereas the doses ofradiation emitted from the radiation sources at both sides thereof (theradiation sources included in the groups 54, 58 or in the groups 156,162) are set at a smaller dose level, of a degree sufficient tosupplement the dose of radiation emitted from the radiation sourcespositioned near the geometric center position.

In the second embodiment, cases are frequent in which an image capturingprocess is carried out with respect to the subject 14, such that thedose of radiation 16 b from the radiation source 18 b in the center ofthe radiation output device 20 is set at a large dose level, whereas thedoses of radiation 16 a, 16 c from the radiation sources 18 a, 18 c atboth sides thereof are set at a smaller dose level, of a degreesufficient to supplement the dose of the radiation 16 b emitted from thecentral radiation source 18 b.

Stated otherwise, during actual image capturing, the control processor124 performs weighting of the radiation doses, such that the doses ofradiation from the radiation sources positioned near the geometriccenter position or from the radiation source in the center of theradiation output device 20 are set at a maximum dose level, whereas thedoses of radiation from the radiation sources at both sides thereof areset at smaller doses, of a degree sufficient to supplement the maximumdose level, and in accordance with such weighting, radiation from eachof the radiation sources is applied simultaneously or sequentially.

In accordance with the aforementioned weighting, upon continued drivingof the respective radiation sources 18 a through 18 i, only theradiation sources positioned near the geometric center position or thecentral radiation source is subject to degradation. Accordingly, fromthe standpoint of service life management of the radiation output device20, it is desirable that dosage management is carried out, so that thecumulative doses (cumulative exposure doses) from each of the radiationsources 18 a through 18 i are respectively the same, and prolonged usagelife of the radiation output device 20 including the respectiveradiation sources 18 a through 18 i can be realized.

Consequently, according to the sixteenth modification, for example, withthe first embodiment, in step S4 and step S11 of FIG. 11, or with thesecond embodiment, in step S33 and step S39 of FIG. 27, data of thedoses of radiation (dose data on which weighting has been carried out)corresponding to optimum radiation dose data retrieved by the databaseretriever 150 are stored in the database 134, and the stored data of therespective radiation doses may serve to assist radiation dosagemanagement and management of service life for the radiation sources 18 athrough 18 i.

As a result, concerning the cumulative exposure dose of radiation, whichis emitted from the respective radiation sources 18 a through 18 i, inthe event that the cumulative exposure dose of the radiation emittedfrom the radiation sources positioned near the geometric center positionor from the central radiation source is more prominent than thecumulative exposure dose of the radiation emitted from the radiationsources at both sides thereof, there is a possibility that the radiationsources positioned near the geometric center position or the centralradiation source may degrade more rapidly than the radiation sourcespositioned at both sides thereof. Consequently, based on comparing eachof the cumulative exposure doses, the control processor 124 changesweighting of the respective radiation doses, such that the doses ofradiation emitted from the radiation sources at both sides thereof areof a maximum dose level, whereas the doses of radiation emitted from theradiation sources positioned near the geometric center position or fromthe central radiation source are of a smaller dose, of a degree forsupplementing the aforementioned maximum dose level, for example, in acase of capturing of images at a large SID.

In this manner, by changing the weighting of the doses of radiationemitted from the radiation sources 18 a through 18 i based on therespective cumulative exposure doses, degradation of only the radiationsources positioned near the geometric center position or the centralradiation source can be avoided, and prolonged usage life of theradiation output device 20 including the respective radiation sources 18a through 18 i can be realized.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made to the embodiments withoutdeparting from the scope of the invention as set forth in the appendedclaims.

What is claimed is:
 1. A radiographic image capturing system comprising:a radiation output device housing therein at least two radiation sourcesfor emitting radiation; a radiation detecting device for detectingradiation that has passed through a subject and converting the detectedradiation into a radiographic image, in a case where each of the atleast two radiation sources applies the radiation to the subject; and acontrol device for controlling the radiation output device and theradiation detecting device, wherein the control device carries outprescribed weighting of doses of radiation to be emitted from the atleast two radiation sources, and controls the radiation output device toapply the doses of the radiation from the at least two radiation sourcesto the subject in accordance with the weighting; wherein the radiationoutput device houses therein at least three radiation sources; the atleast three radiation sources are grouped into at least three groupseach including at least one of the radiation sources; the control devicecarries out, with respect to the groups, the weighting of the doses ofradiation to be emitted from the at least three radiation sources, suchthat the dose of the radiation emitted from the radiation sourceincluded in the group positioned near a geometric center position of theat least three radiation sources is of a maximum dose level, and thedoses of radiation emitted from the radiation sources included in thegroups other than the group positioned near the geometric centerposition are of a lower dose level of a degree for supplementing themaximum dose level; and the control device controls the radiation outputdevice to apply the radiation to the subject from the at least threeradiation sources in accordance with the weighting.
 2. The radiographicimage capturing system according to claim 1, wherein the control devicecomprises: a database storing grouping data for grouping the radiationsources depending on the number of the radiation sources that can behoused in the radiation output device and weighting data for carryingout the weighting of the doses of the radiation with respect to thegroups corresponding to the grouping data; a database retriever forretrieving the grouping data and the weighting data which correspond tothe region to be imaged of the subject from the database; an imagecapturing condition setting unit for setting image capturing conditionsfor irradiating the region to be imaged of the subject with theradiation based on the region to be imaged of the subject and also basedon the grouping data and the weighting data which are retrieved by thedatabase retriever; and a control processor for controlling theradiation output device and the radiation detecting device according tothe image capturing conditions.
 3. The radiographic image capturingsystem according to claim 2, wherein the database further stores optimumradiation dose data representative of optimum radiation doses dependingon a plurality of regions to be imaged and respective thicknesses of theregions; the database retriever retrieves, from the database, theoptimum radiation dose data of a region to be imaged and a thickness,which agree with the region to be imaged of the subject and thethickness of the region to be imaged of the subject, and the groupingdata and the weighting data of the region to be imaged, which agreeswith the region to be imaged of the subject; and the image capturingcondition setting unit sets the image capturing conditions based on theregion to be imaged of the subject and the thickness thereof, and theoptimum radiation dose data, the grouping data and the weighting data,which are retrieved by the database retriever.
 4. The radiographic imagecapturing system according to claim 3, wherein the optimum radiationdose data are stored in the database in association with the regions tobe imaged, the thicknesses thereof, and image capturing techniquesrepresenting orientations of the regions to be imaged with respect tothe radiation detecting device, and directions in which the radiation isapplied to the regions to be imaged; the grouping data and the weightingdata are stored in the database in association with the regions to beimaged and the respective image capturing techniques for the regions tobe imaged; the database retriever retrieves, from the database, theoptimum radiation dose data of a region to be imaged, a thickness, andan image capturing technique, which agree with the region to be imagedof the subject, the thickness thereof, and the image capturing techniquetherefor, and grouping data and weighting data of a region to be imagedand an image capturing technique, which agree with the region to beimaged of the subject and the image capturing technique therefor; andthe image capturing condition setting unit sets the image capturingconditions based on the region to be imaged of the subject, thethickness thereof, and the image capturing technique therefor, and alsobased on the optimum radiation dose data, the grouping data and theweighting data, which are retrieved by the database retriever.
 5. Theradiographic image capturing system according to claim 4, wherein theimage capturing condition setting unit is capable of changing theoptimum radiation dose data, the grouping data and the weighting data,which are retrieved by the database retriever, depending on orderinformation for requesting a radiographic image of the subject to becaptured, the subject, or the image capturing technique for the subject.6. The radiographic image capturing system according to claim 1, whereinthe radiation output device simultaneously or sequentially applies theradiation from the at least three radiation sources to the subject, orthe radiation output device sequentially applies the radiation from eachof the groups to the subject.
 7. The radiographic image capturing systemaccording to claim 1, wherein: in a case that the number of the groupsis an odd number which is equal to or greater than three, the dose ofradiation emitted from the radiation source of the group including thegeometric center position is of the maximum dose level; and in a casethat the number of the groups is an even number which is equal to orgreater than four, the doses of radiation emitted from the radiationsources of two groups positioned near the geometric center position areof the maximum dose level.
 8. The radiographic image capturing systemaccording to claim 1, wherein the control device carries out additionalweighting of the doses of radiation emitted from the radiation sourcesincluded in the group including at least two of the radiation sources.9. The radiographic image capturing system according to claim 1, whereinin a case that the radiation output device and the radiation detectingdevice face each other, the radiation output device houses therein theat least three radiation sources arranged in a linear array or in atwo-dimensional matrix, with respect to an irradiated surface of theradiation detecting device, which is irradiated with the radiation. 10.The radiographic image capturing system according to claim 1, whereinthe radiation output device and the radiation detecting device compriseportable devices; and the control device comprises a portable terminalor a console installed in a medical organization.
 11. The radiographicimage capturing system according to claim 1, wherein the radiationoutput device includes a grip on a side thereof remote from a side onwhich the radiation is emitted; the grip incorporates therein a grippedstate sensor for outputting a detection signal indicating that the gripis gripped; and the radiation output device permits the at least threeradiation sources to emit the radiation if the gripped state sensoroutputs the detection signal.
 12. The radiographic image capturingsystem according to claim 1, wherein: the radiation output device housestherein at least three radiation sources; the at least three radiationsources are grouped into at least three groups each including at leastone of the radiation sources; the control device carries out, withrespect to the groups, the weighting of the doses of radiation to beemitted from the at least three radiation sources, such that the dosesof radiation emitted from the radiation sources included in the groupspositioned at both sides of a geometric center position of the at leastthree radiation sources are of a maximum dose level, and the dose ofradiation emitted from the radiation source included in the grouppositioned near the geometric center position is of a lower dose levelof a degree for supplementing the maximum dose level; and the controldevice controls the radiation output device to apply the radiation tothe subject from the at least three radiation sources in accordance withthe weighting.
 13. The radiographic image capturing system according toclaim 12, wherein: in a case that the number of the groups is an oddnumber which is equal to or greater than three, the dose of radiationemitted from the radiation source of the group including the geometriccenter position is of a lower dose level; and in a case that the numberof the groups is an even number which is equal to or greater than four,the doses of radiation emitted from the radiation sources of two groupspositioned near the geometric center position are of a lower dose level.14. The radiographic image capturing system according to claim 1,wherein: in a case that a first image capturing process is carried out,in which radiation is applied to the subject from at least one radiationsource from among the at least two radiation sources, the radiationdetecting device detects radiation that has passed through the subject,thereby acquiring a first radiographic image by the first imagecapturing process; and the control device carries out the weighting ofthe doses of radiation to be emitted from the at least two radiationsources so as to supplement an insufficiency in the dose of radiation,in a case that the dose of radiation by the first image capturingprocess shown in the first radiographic image does not reach an optimumdose with respect to the subject, and controls the radiation outputdevice to carry out a second image capturing process, in which therespective radiation is applied to the subject from the at least tworadiation sources, in accordance with the weighting.
 15. Theradiographic image capturing system according to claim 14, wherein thecontrol device comprises an addition processor for producing aradiographic image for use in image interpretation of the subject, byadding together digital data of the first radiographic image and digitaldata of a second radiographic image in a case that the radiationdetecting device has acquired the second radiographic image in thesecond image capturing process.
 16. The radiographic image capturingsystem according to claim 14, wherein, in a case that the radiationoutput device houses therein three radiation sources, the control devicecarries out, based on the first radiographic image, the weighting of thedoses of radiation to be emitted from the three radiation sources, suchthat the dose of the radiation emitted from a central one of theradiation sources is of a maximum dose level, and the doses of radiationemitted from the radiation sources at both sides of the central sourceare of a lower dose level, or such that the doses of radiation emittedfrom the radiation sources at the both sides thereof are of a maximumdose level, and the dose of the radiation emitted from the central oneof the radiation sources is of a lower dose level.
 17. The radiographicimage capturing system according to claim 14, further comprising a bodymotion detector for detecting body motion of the subject which has beenpositioned with respect to the radiation detecting device, wherein thecontrol device includes an exposure permission determining unit fordetermining whether radiographic image capturing with respect to thesubject is permitted or interrupted, based on the detection result ofthe body motion detector.
 18. A radiographic image capturing methodcomprising the steps of: wherein in a case that at least two radiationsources for emitting radiation are housed in a radiation output device,carrying out weighting of doses of radiation to be emitted from the atleast two radiation sources; applying the radiation to the subject fromthe at least two radiation sources in accordance with the weighting; andwith the radiation detecting device, detecting the radiation that haspassed through the subject and converting the detected radiation into aradiographic image, wherein the radiation output device houses thereinat least three radiation sources; the at least three radiation sourcesare grouped into at least three groups each including at least one ofthe radiation sources; the control device carries out, with respect tothe groups, the weighting of the doses of radiation to be emitted fromthe at least three radiation sources, such that the dose of theradiation emitted from the radiation source included in the grouppositioned near a geometric center position of the at least threeradiation sources is of a maximum dose level, and the doses of radiationemitted from the radiation sources included in the groups other than thegroup positioned near the geometric center position are of a lower doselevel of a degree for supplementing the maximum dose level; and thecontrol device controls the radiation output device to apply theradiation to the subject from the at least three radiation sources inaccordance with the weighting.